Grzimek's Animal Life Encyclopedia_ Mammals ( PDFDrive ) (1)

Vol. 16: Mammals V Subfamily: Rats, mice, and relatives I

Steppe lemming BEHAVIOR

Lagurus lagurus Mainly nocturnal, but occasionally diurnal also. It lives in bur-
row systems that can join up to cover large areas. Populations
TAXONOMY fluctuate and they can be exceedingly numerous in some years.

Lagurus lagurus (Pallas, 1773), Kazakhstan. FEEDING ECOLOGY AND DIET

OTHER COMMON NAMES Seeds, foliage, shoots, and roots.

None known. REPRODUCTIVE BIOLOGY

PHYSICAL CHARACTERISTICS They can produce up to five litters of young each year, with as
many as 12 young in a litter. Pregnancy lasts around 20 days
Head and body length 3.5–5.5 in (9–14 cm); weight 0.5–1 oz and the young are reproductive by 30–45 days old.
(10–25 g). Upperparts light gray to cinnamon gray, underparts
whitish. Black stripe along spine. CONSERVATION STATUS

DISTRIBUTION Not threatened.

Central Asian steppes from the Ukraine to China. SIGNIFICANCE TO HUMANS

HABITAT A serious pest of crops and grazing pastures when populations
are high. ◆
Open grassland steppe, semi-deserts, and cultivated fields.

Common name / Physical Habitat and Distribution Diet Conservation
Scientific name characteristics behavior status
White-footed vole
Arborimus albipes Pelage is long, fine, dark brown. Under- Close to small streams and Pacific coastal zone Roots, wide variety of Data Deficient
parts are white, gray, or pinkish buff. Tail
Southern red-backed vole is long, ears are small, feet are long. are often found near fallen south of Columbia leaves from those of Not threatened
Clethrionomys gapperi Head and body length 3.7–4.3 in (9.5–
11 cm), tail length 2.3–3.4 in (6– trees from sea level to over River, from western grasses to deciduous Not threatened
Northern collared lemming 8.7 cm), weight 0.8–0.9 oz (25–26 g).
Dicrostonyx groenlandicus 3,280 ft (1,000 m). Most Oregon to extreme trees, mosses, and Not threatened

Sagebrush vole abundant in deciduous forest. northwestern California, pollen.
Lemmiscus curtatus
Reproduce throughout the United States.
[continued]
year, mean litter size is three.

Arboreal, nocturnal.

Dense, long, soft fur that is dark gray Cool, mossy, and rocky boreal Most of Canada from Leaf petioles, young
above and chestnut brown stripe running
along back from head to tail. Face and forests in both dry and moist northern British shoots, fruits, berries,
sides are yellowish brown, underparts
are dark slate gray to almost white. Head areas, as well as tundra and Columbia to Labrador, bark, roots, lichens,
and body length 2.7–4.4 in (7–11.2 cm),
tail length 0.9–3.4 in (2.5–6 cm). bogs. Active during day and excluding Newfound- fungi, and insects.

night. Construct spherical land; south in the

nests. Appalachians to

northern Georgia, in the

Great Plains to northern

Iowa, and in the

Rockies to central New

Mexico and east-central

Arizona, United States.

Short, stocky, heavy year-round coat that Tundra. Is generally Northern Greenland Willow buds, fruits,
varies seasonally in color. Light to dark terrestrial, but has been seen and Queen Elizabeth flowers, grasses, and
gray with buffy to reddish brown tone. in the water. Burrows lead to Islands, south to Baffin twigs.
Dark lines run down back and on sides nests that are protected by and Southampton
of head. Winter coat is white. Head and males. islands and north-
body length 3.9–6.1 in (10–15.7 cm), tail eastern District of
length 0.4–0.8 in (1–2 cm), weight 1–4 oz Keewatin, Canada.
(30–112 g).

Pale gray and buff dorsally, ventral side Areas largely dominated by Southern Alberta and Flower and fleshy parts
is silver, white, and buff. Fur is dense, bunch grasses and
long, and soft. Body is stocky with short sagebrush, including semi- southeastern of vegetation.
tail, stout claws, and small ears. Head arid prairies, brushy
and body length 3.5–5.1 in (9–13 cm), canyons, and rolling hills Saskatchewan, Canada,
tail length 0.6–1.2 in (1.6–3 cm). with loose soil. Active
throughout day and year. south to northwestern
Occur in pairs or are solitary.
Colorado and east-

central California,

including the Columbia

Basin of interior Oregon

and Washington,

United States.

Grzimek’s Animal Life Encyclopedia 237

Subfamily: Rats, mice, and relatives I Vol. 16: Mammals V

Common name / Physical Habitat and Distribution Conservation
Scientific name characteristics behavior Diet status
Rock vole
Microtus chrotorrhinus Ventral color is grayish brown on the Among mossy rocks and Southern Labrador Mainly bunchberry. Not threatened
back, face is orange, rich yellow around boulders in forests with southwest through
Meadow vole the nose. Winter coat is longer and moderately open canopies southern Quebec and
Microtus pennsylvanicus glossier. Moderately large with sparsely and a rich herbaceous under Ontario, Canada, to
haired tail. Underparts are slightly paler, story. Primarily diurnal, good northeastern
Woodland vole ears are large. Head and body length nest builder. Low survival Minnesota, United
Microtus pinetorum 5.5–7.3 in (14–18.5 cm), weight 1–1.7 rate of young. States; south in
oz (30–48 g). Appalachian Mountains
Round-tailed muskrat to eastern Tennessee
Neofiber alleni and western North
Carolina, United States.
Western heather vole
Phenacomys intermedius Dorsal surface is dark blackish brown to Meadows, lowland fields, From central Alaska to Fresh grass, sedges, Not threatened
dark reddish brown with coarse black grassy marshes, and along the Atlantic Coast. and herbs, as well as a
Northern bog lemming hairs. Ventral surface is gray or white. rivers and lakes. Active South of the Canadian variety of seeds and
Synaptomys borealis Head and body length 5–7.7 in (12.8– during all times of day. border, western limit is grains.
19.5 cm), tail is about 40% of body Females are territorial. the Rocky Mountains.
length. Promiscuous. Found as far south as
New Mexico and
Georgia, United States.

Dorsal varies from light to dark brown, Deciduous forests in eastern Eastern U.S. shoreline Tubers, roots, seeds, Not threatened
ventral side is whitish or silvery. Head North America. Form mono- from southern Maine leaves, and nuts, as well
and body length 3.2–4.7 in (8.3–12 cm), gamous pairs. One to 13 off- to northern Florida, as berries and insects.
tail length 0.6–1.6 in (1.5–4 cm). spring per litter. west to central Wiscons
in and eastern Texas.

Outer fur is composed of coarse guard Wet moist areas on mainland Most of peninsular Aquatic grasses as well Lower Risk/Near
hairs and is dark brown and glossy in and islands. Construct dome- Florida to extreme as roots, stems, and Threatened
color. Undercoat is dense, becoming gray shaped lodges. Nocturnal. southeastern Georgia, seeds.
at base. Tail is round. Head and body United States.
length 15–21 in (38.1–54.6 cm).

Fur is long, soft, and varies In stands of spruce, lodge- Southwestern British Leaves and fruits of Not threatened
geographically. Dorsal fur is generally pole pine, aspen, and grassy
brown to grayish, ventral side is gray. meadows in montane forest, Columbia and adjacent willows, myrtle
Feet are white to gray, ears are orange. subalpine, and alpine tundra.
Head and body length 5–5.5 in (13–14 Active year round, does not Alberta, Canada, south blueberry, snowberry,
cm), weight 1–1.7 oz (30–50 g). hibernate. Solitary, except
during breeding season. to northern New bog birch, kinnikinnik

Mexico, central Utah, (bearberry) in the

and northern California, summer months. The

United States; disjunct rest of the year, they

populations in east- feed on bark and buds

central California and of willow, birch, and

western Nevada. blueberry trees.

Stocky build with short legs and long tail. In burrows among sedges Alaska to northern Sedges and grasses. Not threatened
Ears are small, nose is blunt. Pelage is and grasses where water
coarse and ruffled, and varies from level is high. Breeding Washington, United
grayish brown to chestnut brown, under- season is from May to
side is pale gray. Tail is brown above and August, litters contain two States, eastwards
white below. Head and body length 4.8– to eight individuals.
5.5 in (12.2–14 cm), tail length 0.7–1 in across much of interior
(2–2.7 cm), weight 0.9–1.2 oz (27–35 g).
Canada to Labrador;

disjunct range segment

from Gaspe Peninsula,

Quebec, to central New

Hampshire, United

States.

Resources Mitchell-Jones, A. J., et al. The Atlas of European Mammals.
London: Academic Press, 1999.
Books
Carleton, M. D., and G. G. Musser. “Muroid Rodents.” In Nowak, R. M. Walkers Mammals of the World. 6th ed.
Baltimore and London: Johns Hopkins University Press,
Orders and Families of Recent Mammals of the World, edited 1999.
by S. Anderson and J. K. Jones Jr. New York: John Wiley
and Sons, 1984. Wilson D. E., and S. Ruff, eds. The Smithsonian Book of North
American Mammals. Washington, DC: Smithsonian Institute
Corbett, G. B. The Mammals of the Palaearctic Region: A Press, 1999.
Taxonomic Review. London: British Museum (Natural
History), 1978. Mike J. R. Jordan, PhD

238 Grzimek’s Animal Life Encyclopedia

᭝

Rats, mice, and relatives II

Hamsters (Cricetinae)

Class Mammalia
Order Rodentia
Suborder Sciurognathi
Family Muridae
Subfamily Cricetinae

Thumbnail description
Hamsters are mouse-like Old World rodents with
chunky bodies; short, furry tails; and large cheek
pouches, used to transport food; they have
dexterous forepaws with four digits plus a “thumb
knob”; hind feet have five digits; individual
hamsters live alone in underground burrows, are
active at night, and hibernate in winter

Size
2–13.4 in (5–34 cm); 0.9–31.7 oz (25–900 g)

Number of genera, species
7 genera; 18 species

Habitat Distribution
Deserts, dry plains, steppes, and cultivated Throughout the Palearctic zone of Europe and Asia
fields

Conservation status
Endangered: 2 species; Vulnerable: 1 species;
Lower Risk/Near Threatened: 4 species

Evolution and systematics Physical characteristics

Members of the group Cricetinae appear in the European Dwarf hamsters, genus Phodopus, are the smallest members
fossil record in the Middle Miocene (11.2 to 16.4 million years of the group, averaging 2–4 in (5.3–10.2 cm) in length; the
ago [mya]) and in the Asian fossil record in the late Miocene largest hamster is the black-bellied hamster, Cricetus cricetus,
(6 to 11 mya). As of 2003, 15 extinct fossil genera have been which at 7.9–13.4 in (20–34 cm) is about the size of a large
documented. rat or guinea pig.

Hamsters are related to voles, lemmings, and New World Described as “all head and rump,” hamsters have stout bod-
mice. In the mid-twentieth century, taxonomists split the ies and short legs and tails. The feet are wide, sometimes furry;
group from the Muridae as a separate family, Cricetidae; how- the body fur is soft and thick and varies in color (depending
ever this split has been reversed. on species) from gray to reddish brown; underparts can be
white, gray, or black. Most hamsters have large cheek pouches.
The number of genera in Cricetinae is still debated. Some
taxonomists place Calomyscus and/or Mystromys in this group; Unusual for small mammals, the hamster stomach has two
others place these two genera in their own subfamilies. compartments; the forestomach, or cardiac stomach, has tough
keratin as a structural component and is non-glandular, simi-
Some sources specify 18 species in 7 genera, while others lar in structure and function to the rumen of cattle and other
describe 24 species in 5 genera. According to the Wilson and grazing animals. The second compartment—the pyloric, or
Reeder classification for 18 species in 7 genera, the rat-like glandular, region—is separated from the forestomach by mus-
hamsters, genus Cricetulus, include six Eurasian species; the cular folds.
golden hamsters, genus Mesocricetus, include four European
and Middle Eastern species; the dwarf hamsters, genus Phodo- Hamsters have excellent hearing and an acute sense of
pus, include three Asian species; the Mongolian hamsters, smell; some species have scent glands on their flanks and use
genus Allocricetulus, include two Asian species; with the Can- scent to mark their territories.
sumys genus having only one species, the Gansu hamster.
Black-bellied hamsters are also the sole species in genus Distribution
Cricetus, as well as the greater long-tailed hamster in genus
Tscherskia. The group is widely distributed in Eurasia, although a few
species—the golden hamster is one example—have quite re-
Grzimek’s Animal Life Encyclopedia
239

Subfamily: Rats, mice, and relatives II Vol. 16: Mammals V

Cricetus cricetus female taking newborn pups in her mouth. (Illustra- A Dzhungarian (Rissoam dwarf) hamster (Phodopus sungorus). (Photo
tion by Wendy Baker) by © Leach/OSF/Animals Animals. Reproduced by permission.)

stricted ranges. In the northern part of Eurasia, hamsters are Some species hibernate continuously, while others enter
found from central Europe through Siberia to northern China shallow daily torpor during the winter. In winter, rat-like
and Korea. In the south, various species occur from Syria to hamsters do not hibernate continuously but awaken from time
Pakistan. to time to eat stored food. Hibernation for uninterrupted pe-
riods of up to 28 days has been experimentally induced in the
Habitat golden hamster through exposure to cold. The mouse-like
hamster is active only at night during the summer, but it is
Most hamsters live in dry, open habitats such as desert bor- also active by day in the autumn and winter.
ders, short-grass steppes, and rocky foothills, although the
black-bellied hamster sometimes digs burrows along river- Hamsters have a poor sense of sight despite their large pro-
banks. With the spread of agriculture, many species have truding and round eyes. This is compensated by their well-
moved into cultivated lands. developed sense of hearing that allows them to hear a wide
range of sounds, including sounds in the ultrasonic frequen-
Behavior
Hibernating hamsters in their nest chamber. (Illustration by Wendy
Hamsters are active rodents with bodies well suited for Baker)
running and digging. Most excavate their own burrows (some
occupy burrows abandoned by—or still occupied by—other Grzimek’s Animal Life Encyclopedia
rodents). All are nocturnal and range far from their burrows
at night to collect food that they carry home in large, inter-
nal cheek pouches. Inside the burrow, where special cham-
bers are reserved for food storage, they stroke cheeks with
paws to force the seeds out. In winter, hamsters hibernate if
temperatures are sufficiently cold.

Some hamsters are gregarious, even highly social, while
others tend to live alone or in pairs. Phodopus may be pair-
bonded; paternal care is unusual in hamsters and only Phodo-
pus can be kept as mated pairs. Where burrows are closely
spaced, this is only because appropriate habitat, soil loose and
deep enough for digging, is in limited supply. Hamsters are
fierce for their size and very aggressive to members of their
own species. Pet golden hamsters must be maintained soli-
tary. In addition to taking prey such as smaller rodents or
baby birds the larger hamster species will attack humans and
dogs when threatened.

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Vol. 16: Mammals V Subfamily: Rats, mice, and relatives II

A male golden hamster (Mesocricetus auratus). (Photo by Carolyn A.
McKeone/Photo Researchers, Inc. Reproduced by permission.)

A black-bellied hamster (Cricetus cricetus) foraging in grass. (Photo by
Hans Reinhard/Okapia/Photo Researchers, Inc. Reproduced by per-
mission.)

cies, which helps them communicate with each other without
being heard by other animals. Hamsters also have an acute
sense of smell and can distinguish one another by their dis-
tinct scents. Olfactory communication has been shown to play
an intricate role in the daily activities of the golden hamster.
Olfaction allows these nocturnal, burrowing, solitary, and ter-
ritorial animals to communicate important individual infor-
mation to one another and to receive information from their
environment.

Feeding ecology and diet A 20-day-old hamster. (Photo by Carolyn A. McKeone/Photo Re-
searchers, Inc. Reproduced by permission.)
Living in dry, comparatively unproductive habitats, ham-
sters often travel long distances in search of food. Besides car- 241
rying seeds and grain in their roomy cheek pouches, they carry
large items such as root vegetables in their teeth. By storing
food, hamsters make sure they will have enough to eat when
food is in short supply—especially in winter.

Hamsters eat frequently throughout the day; their mixed
diet is mostly seeds and grains but also includes green plant
parts along with insects such as moths, beetle larvae, earth-

Grzimek’s Animal Life Encyclopedia

Subfamily: Rats, mice, and relatives II Vol. 16: Mammals V

A Dzhungarian hamster (Phodopus sungorus) gathers nesting mater-
ial. (Photo by Kenneth W. Fink/Photo Researchers, Inc. Reproduced
by permission.)

The Dzhungarian hamster (Phodopus sungorus) will fill its cheeks with
food to carry to its burrow. (Photo by © Jorg & Petra Wegner/Animals
Animals. Reproduced by permission.)

worms, and grasshoppers. Some hamsters kill smaller ro-
dents, lizards, frogs, or baby birds, and they will eat carrion
as well.

Reproductive biology

Hamster are sexually mature at a very young age, soon af-
ter they are weaned. Typically, males and females come to-
gether only to mate. The gestation period is quite short,
ranging from 17 to 22 days. Litter size ranges from one to 16
pups with the average litter size around 11; females have eight
to 17 nipples depending on species. In the wild hamsters may
have two to four litters per year but species kept in captivity
reproduce more frequently.

Hamsters are born hairless, with their eyes and ears closed
and legs still somewhat undeveloped. The young do have teeth
at birth, however, and eat solid food at seven to 10 days. They
are weaned at 21 days.

Though most male hamsters play no role in raising the
young, male Dzhungarian hamsters (Phodopus sungorus) are at-

242 Grzimek’s Animal Life Encyclopedia

Vol. 16: Mammals V Subfamily: Rats, mice, and relatives II

tentive fathers that assist at births, lick newborns clean, help Significance to humans
keep them warm, and care for them when the female leaves
the nest to feed. Like their mouse relatives, most hamsters Humans have long regarded hamsters as agricultural pests.
live one to three years. Large species, particularly Cricetus cricetus, have been trapped
for their fur; as recently as 2001, hamster fur made headlines
Conservation status as a controversial high-fashion item. Historically, farmers
from China to Germany dug up hamster burrows to get at
Threats to hamsters include loss of habitat, widespread the stored grain—sometimes to feed farm animals, and some-
use of rodenticides on farms, and, formerly, trapping for fur times—when times were hard—to feed themselves.
and as a pest-control measure. According to the IUCN Red
List of 2002, two species are classified as Endangered: the Since the twentieth century hamsters have been most im-
golden hamster, Mesocricetus auratus of Syria, and the Hot- portant to humans as a biomedical research animal. Chinese
son’s mouse-like hamster, Calomyscus hotsoni of Pakistan. Four hamsters were the first species to be used in laboratory re-
species are classified as Lower Risk/Near Threatened: the search, in 1919. As of 2002, eight different species have been
gray hamster, Cricetulus migratorius; the Afghan mouse-like used in research on infectious diseases, cytogenetics, toxi-
hamster, Calomyscus mystax ; Tsolov’s mouse-like hamster, C. cology, and oncology, as well as obesity and diabetes, pho-
tsolovi; and the Urartsk mouse-like hamster, C. urartensis; one toperiod changes, social behavior, and hibernation physiology.
species is classified as Vulnerable, the Romanian hamster, The species most widely used in research is the golden ham-
Mesocricetus newtoni. ster.

Hamsters are also very popular pets; they are also bred for
specialized colors and patterns, entered in shows, and exhib-
ited at zoos.

Grzimek’s Animal Life Encyclopedia 243

1
2

1. Black-bellied hamster (Cricetus cricetus); 2. Golden hamster (Mesocricetus auratus). (Illustration by Wendy Baker)
244 Grzimek’s Animal Life Encyclopedia

Vol. 16: Mammals V Subfamily: Rats, mice, and relatives II

Species accounts

Black-bellied hamster these clusters are not true colonies; like most hamsters, mem-
bers of this species are solitary in their habits. They are also
Cricetus cricetus active nocturnally and hibernate in winter. Winter burrows can
be very deep, extending more than 6 ft (2 m) below the soil
SUBFAMILY surface. Cricetus burrows are particularly complex, with several
entrance tunnels, numerous chambers for nesting and food
Cricetinae storage, and a dead-end tunnel used as a toilet area. The size
of the burrow is correlated with the hamster’s age; old females
TAXONOMY with young have the most complex burrows.

Cricetus cricetus (Linnaeus, 1758), Germany. Black-bellied hamsters live in regions that can be quite cold
in winter; they hibernate but wake up every 5–7 days to feed
OTHER COMMON NAMES on their stored supplies. The length of hibernation is influ-
enced by weather and other factors but typically occurs from
English: Common hamster, European hamster, field hamster. the end of September through April.

PHYSICAL CHARACTERISTICS When the hamster population in a given area reach a very
high density, some members of the population become rest-
The largest hamster, 8–12 in (20–34 cm) long; males larger less and leave, spreading out into new locations. Capable of
than females (10.5–12.5 in [27–32 cm] versus 8.7–9.8 in [22–25 swimming, the hamsters sometimes cross large rivers during
cm]). Tail short and hairless, 1.6–2.4 in (40–60 mm). Weight these wanderings.
4.5–36.3 oz (112–908 g), averaging 18 oz (450 g) for males and
14 oz (350 g) for females. Thick fur is reddish brown above FEEDING ECOLOGY AND DIET
with white patches on the flanks, nose, cheeks, and throat, and
black underparts—unusual in mammals. Color variations, from As with most hamsters the diet includes grains, beans, roots,
albino to melanistic, are common. and the green parts of plants; black-bellied hamsters also eat
insect larvae—especially beetle larvae—frogs, earthworms, and
DISTRIBUTION field mice. They often store very large quantities of cereal
grains, seeds, peas and potatoes in their winter burrows; there
Black-bellied hamsters live in lowlands of central and Eastern are reports of burrows containing as much as 198 lb (90 kg) of
Europe, from Belgium to the Altai region of Siberia. food.

HABITAT REPRODUCTIVE BIOLOGY

Throughout much of their range, the hamsters’ natural steppe Most breeding activity takes place between June and August,
habitat has been converted to agricultural land; they have although breeding can begin earlier or continue later, depend-
adapted to living in and along farm fields, especially where ing on location and climate. Probably serially monogomous. A
both grain and root crops are grown. Occasionally, they dig courting male will enter the female’s territory and mark the
burrows along riverbanks. These hamsters generally prefer low area with secretions from glands in his flanks. A lengthy
elevation habitat but can found up to an altitude of 2,000 ft courtship ritual ensues, in which the male runs after the fe-
(610 m). male, making a loud sniffing noise that serves as his mating
call. After mating occurs, the female becomes aggressive and
BEHAVIOR drives the male away. (In captivity, however, male black-bellied
hamsters sometimes help to raise the young.)
When suitable burrowing sites are in short supply, black-
bellied hamsters may burrow quite close together; however The female cushions the floor of the nest chamber with
grass stalks. The gestation period is 18–20 days. A typical lit-
Mesocricetus auratus ter is 4–12 pups; the female has eight nipples and usually raise
Cricetus cricetus no more than eight young. Newborns weigh about 0.2 oz (7
g). They start to eat solid food at one week, when their eyes
Grzimek’s Animal Life Encyclopedia are still closed; at age two weeks they open their eyes and have
acquired a full coat of fur. At three weeks they are weaned;
they will reach adult size at eight weeks. A female typically
has two litters per year in the wild. These are comparatively
long-lived hamsters, sometimes reaching the age of eight
years old.

CONSERVATION STATUS

Sometimes considered a serious pest on farms, black-bellied
hamsters in the twentieth century were often systematically
poisoned with rodenticides. This practice, combined with
habitat loss, due both to changes in farming practices and

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Subfamily: Rats, mice, and relatives II Vol. 16: Mammals V

spreading industrial construction, has led serious population around irrigation wells; all of the burrows were in sandy clay
declines in some locations. As of 2000, this hamster was pro- soil overlaying limestone bedrock.
tected under the European Community Habitats Directive as
a threatened species in Germany, Belgium, the Netherlands, BEHAVIOR
France, and Austria. They are also protected in Bulgaria,
Croatia, and Slovenia, where they are uncommon, not be- Though mostly nocturnal, golden hamsters are sometimes ac-
cause of human actions, but because they are at the edge of tive in daytime. Burrow depths measured on the 1999 expedi-
their range. tion ranged from 14 to 41.3 in (36 to 106 cm), averaging about
25.4 in (65 cm). Burrow entrances averaged 1.6–2.0 in (4–5
SIGNIFICANCE TO HUMANS cm) in diameter and led to vertical entrance tunnels. Occupied
burrows had their entrances plugged with lumps of earth
As land was increasingly cleared for farming in the Middle slightly below the soil surface. Nest chambers ranged from
Ages, this probably created conditions favorable for hamsters 2.9–7.8 in (10–20 cm) wide; the spherical nests were made of
and led to a rise in populations. Historically this species has dry plant materials. In contrast to black-bellied hamster bur-
been widely hunted for food and trapped for its colorful fur, rows, which are complex and often have more than 10
which was used to make clothing or as a warm lining; as of branches, a golden hamster’s burrow is relatively simple, with
2001 hamsters were still being trapped in eastern European na- few side tunnels. This species reserves a blind-end tunnel for
tions where they are common, such as Hungary, and the fur urination but defecates throughout the burrow. They are
was still being used in some high-fashion garments. thought to hibernate in winter from November to February,
although the hibernation state is not total. In the lab, hiberna-
Black-bellied hamsters have historically been a particular tion can be induced at temperatures below 46°F (8°C). Preda-
pest in corn fields; corn is often the last crop to be harvested, tors are uncommon in the are where these hamsters occur
so hamsters from neighboring fields congregate in corn fields (because of the dense human population) but in 1999 hamster
after their other food sources are gone. It’s worth noting that remains were found in a barn owl pellet.
this species can also be helpful to farmers because it hunts
field mice and insect pests. FEEDING ECOLOGY AND DIET

Finally, the black-bellied hamster is sometimes used as a Although lab diets have been carefully worked out, very little is
lab animal, particularly in oncology research. ◆ known about how these hamsters live in the wild.

Golden hamster REPRODUCTIVE BIOLOGY

Mesocricetus auratus In the wild the breeding season is thought to begin in Febru-
ary (lab animals breed year round). Males and females meet
SUBFAMILY only to breed and the males do not assist in rearing the
young. The female’s estrous cycle is four days long and estrus
Cricetinae lasts 27.4 hours. After conception the gestation period is usu-
ally 16 (but sometimes up to 19) days. The litter size can
TAXONOMY range from one to 16 pups; litters of six to nine are typical.
The pups are blind and hairless at birth and typically weigh
Mesocricetus auratus (Waterhouse, 1839), Aleppo, Syria. 0.07–0.1 oz (2–3 g); they grow quickly, are weaned by 20 days,
and are sexually mature and ready to breed at 7–8 weeks old.
OTHER COMMON NAMES If she feels threatened, the mother may transport her young in
her cheek pouches (this occurs only during their first three
English: Syrian hamster; Syrian golden hamster. days of life).

PHYSICAL CHARACTERISTICS CONSERVATION STATUS

Medium sized, about 6–7 in (15–18 cm) long, stubby white or This species is listed as Endangered.
pink tail is 1.2 cm (0.5 in); weight 3–4 oz (90–120 g), with fe-
males larger than males. Fur is light reddish brown to golden SIGNIFICANCE TO HUMANS
with white or cream-colored underparts; domesticated animals
have been bred for a wide variety of colors, patterns, and fur Among endangered species, golden hamsters are unusual in
textures. Cheek pouches are very large, extending back behind that humans may have helped to prevent the species from be-
the shoulders. Females have 12–17 nipples. Life span is 2–3 coming extinct by taking animals from the wild to use in bio-
years. medical research. The story begins in 1930, when four juvenile
animals were taken from a burrow in a Syrian wheat field in
DISTRIBUTION 1930 and brought to the Microbiological Institute of
Jerusalem, with the goal of using them instead of Chinese
Although some accounts assert that this species is extinct in the hamsters, which had failed to breed in captivity in a study of
wild, it may in fact be locally common; specimens were col- the disease Leishmaniasis. The golden hamsters reproduced very
lected in the Mount Aleppo region, in northwestern Syria in well in captivity; their descendents, along with the descendents
1999; other specimens were sighted near Jarablus in Syria in of another 12 animals collected in 1971, have been distributed
1986 and near Gaziantep in Turkey, mostly recently in 1999. to research institutions all over the world. Although as of 2003,
eight hamster species are used in research, golden hamsters are
HABITAT by far the most the most common experimental subject; in ad-
dition, they are the most popular of all the hamster species
Historically, this hamster’s native habitat has been described as kept as pets. Escaped pets have established wild populations in
dry, rocky steppe or brushy slopes. The wild population dis- some locations in the British Isles.
covered in 1999 was living in agricultural fields planted with
annual crops including barley, chickpeas, lentil, melons, toma- Despite their endangered status, in Syria the remnant wild
toes, and others; hamsters were most often found on plots of populations are still considered as pests and trapped or poi-
legumes. Burrows were also found on the embankments
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246

Vol. 16: Mammals V Subfamily: Rats, mice, and relatives II

soned using rodenticides provided by the government. Farm- are turned out to graze in any remaining fields. At this time
ing practices are another problem. In May and June fields are it may be hard of hamsters to find cover, nutrition, or the ex-
harvested, then burned or ploughed under; meanwhile sheep tra food they need to store for the winter. ◆

Common name / Physical Habitat and Distribution Conservation
Scientific name/ characteristics behavior Diet status
Other common names

Mongolian hamster Back is yellowish gray, belly is off-white. Dry steppes, forests, fields, Steppes of Mongolia Cereals and various Not threatened
Allocricetulus curtatus Lacks typical pectoral spot, young are and gardens. north of the Altai and seeds of wild plants.
German: Mongolische completely gray, later turning grayish eastwards to Inner
Zwerghamster; Spanish: yellow. Head and body length 4.3–5.9 in Mongolia.
Hámster enano de Mongolia (11–15 cm).

Eversmann's hamster Upperparts dark brown or reddish sand, Desert or steppe habitats, as Northern Kazakhstan Cereals and fruits, as Not threatened
Allocricetulus eversmanni underparts are gray or white. There is a well as cultivated areas in the steppes from Volga well as insects, spiders,
German: Eversmann- brownish gray or reddish brown spot on vicinity of the Caspian Sea River to the upper and snails.
Zwerghamster; Spanish: the chest. Small eyes, ears, and limbs. and south of the region. Irtysh at Zaysan.
Hámster enano de Eversmann Head and body length 5.9–7.4 in (15–
19 cm).

Greater long-tailed hamster Back is dark brown, belly is off-white to Humid zones, fens, valleys, Northeastern China Cereals, such as wheat, Not threatened
Tscherskia triton gray. Dark ears, sometimes with white
German: Zwerghamster; edges. Extended snout. Head and body as well as forests full of hazel from Shaanxi to south- oats, barley, and maize,
Spanish: Hámster-rata enano length 7–9.8 in (18–25 cm), tail length
2.7–3.9 in (7–10 cm). trees at low elevations. eastern Manchuria as well as cherries, nuts,

Breeding season from May (Heilongjiang) and and acorns.

to October. Four to five litters south to Anhui, Korea,

per year, averaging seven and north to upper

young per litter. Ussuri in Russia.

Gray dwarf hamster Fur is long, mouse gray in color. May be Open dry country, such as Southern European Young shoots and seeds. Lower Risk/Near
Cricetulus migratorius Russia and south- Threatened
German: Graue Zwerghamster; reddish or buffy. Underparts are light steppes and the borders of eastern Europe (Greece,
Spanish: Hámster armeno Romania, Bulgaria)
gray or white. Robust body, blunt muzzle, deserts. In Afghanistan, through Kazakhstan to
southern Mongolia and
short legs and tail, large internal cheek occurs at 1,310–11,810 ft northern China
(Xinjiang, Ningxia; Qin),
pouches. Head and body length 3.1–9.8 (400–3,600 m) on rocky north nearly to Moscow,
south to Israel, Jordan,
in (8–25 cm), tail length 0.9–4 in (2.5– slopes and plateaus almost Lebanon, Iraq, Iran,
Pakistan, Afghanistan,
10.6 cm). devoid of vegetation. and Turkey.

Nocturnal in winter, diurnal

in summer. Live in burrows.

Extremely aggressive.

Striped dwarf hamster Fur is long, mouse gray in color. May be Open dry country, such as Steppes of southern Young shoots and seeds. Not threatened
Cricetulus barabensis Siberia from River
German: Daurischer reddish or buff. Underparts are light gray steppes and the borders of Irtysh to Ussuri region,
Zwerghamster; Spanish: and south to Mongolia,
Hámster listrado chinês or white. Dark brown dorsal stripe. deserts. Nocturnal in winter, northern China
(Xinjiang through Nei
Robust body, blunt muzzle, short legs diurnal in summer. Live in Mongol), and Korea.

and tail, large internal cheek pouches. burrows. Extremely

Head and body length 3–10 in (8–25 cm), aggressive.

tail length 0.9–4.1 in (2.5–10.6 cm)

Brandt's hamster Upperparts are light reddish brown, Dry, rocky steppes or brushy Anatolian Turkey, south Green vegetation, meat, Not threatened
Mesocricetus brandti underparts are white or creamy. Skin is slopes. Nocturnal. Maximum into Israel, Lebanon, seeds, and fruit.
English: Turkish hamster loose, enormous cheek pouches. Head of two litters per year. Syria, northern Iraq,
and body length 6.6–7 in (17–18 cm), northwestern Iran,
tail length 0.4 in (1.2 cm). northern Transcaucasia,
and Kurdistan.

Dzhungarian hamster Thick body, short tail, cheek pouches. Semi-arid areas, usually Eastern Kazakhstan and Seeds and any available Not threatened
Phodopus sungorus Grayish or pinkish buff. Dorsal stripe grassy plains, sand dunes, or southwestern Siberia. plant matter.
German: Zwerghamstern; runs along length of body. Underparts wormwood steppes. Solitary,
Spanish: Hámster ruso and muzzle, upper lips, limbs, and tail are except for breeding. Nests
white. Tail and feet are covered with hair. are built in burrows.
Head and body length 2–4 in (5.3–10.2
cm), tail length 0.2–0.4 in (0.7–1.1 cm).

Grzimek’s Animal Life Encyclopedia 247

Subfamily: Rats, mice, and relatives II Vol. 16: Mammals V

Resources Van Hoosier, G. L., Jr., and Charles W. McPherson.
Laboratory Hamsters. New York: Academic Press, 1987.
Books
Periodicals
Baumgart, G. “The European Hamster. Cricetus cricetus L. Gattermann, R., et al. “Notes on the Current Distribution and
(1758) in Alsace. 1. Ancient and Recent Data (1546–1995),
2. Hypotheses on the Cause of its Extinction.” Gerstheim, the Ecology of Wild Golden Hamsters (Mesocricetus
France: Report of the National Office of Hunting 1967. auratus).” Journal of Zoology 254, no. 3 (2001): 359–365.

Nowak, Ronald M. Walker’s Mammals of the World. Vol. 2, 6th Nechay, Gabor. “Status of Hamsters Cricetus cricetus, Cricetus
ed. Baltimore: Johns Hopkins University Press, 1999. migratorius, Mesocicretus newtoni and Other Hamster Species
in Europe.” Nature and Environment 106 (200): 1–73.
Subcommittee on Laboratory Animal Nutrition, Committee on
Animal Nutrition, Board on Agriculture, National Research Cynthia Ann Berger, MS
Council. Nutrient Requirements of Laboratory Animals. Fourth
Revised Edition. Washington, DC: The National Academy
of Sciences, 1995.

248 Grzimek’s Animal Life Encyclopedia

᭝

Rats, mice, and relatives III

Old World rats and mice (Murinae)

Class Mammalia
Order Rodentia
Suborder Sciurognathi
Family Muridae
Subfamily Murinae

Thumbnail description
Old World rats and mice can grow up to the size
of rabbits and have long tails, either furry or
scaly, sometimes longer than the body itself;
aquatic species may use their tails as rudders
and others use their tails and unique opposable
digits on their front feet to climb; characteristics
vary widely, but all Murinae have a row of
tubercles on the inside of their upper molars

Size Distribution
1.9–14.7 in (5–36 cm); 0.2–52.9 oz (5–1,500 g) Worldwide

Number of genera, species
122 genera; 529 species, with more identified
annually

Habitat
Forests, fields, bushes, flatlands, steppes, etc.;
some are aquatic, some live in burrows,
tunnels, beneath logs or other forms of shelter,
or in nests; also can live in trees, in sewers
and cellars, and in various parts of houses

Conservation status
Critically Endangered: 18 species; Endangered:
33 species; Vulnerable: 56 species

Evolution and systematics

The Muridae family contains 25% of all living mammals,
and it appeared in the fossil record during the Upper Miocene
(10–15 million years ago [mya]). Recent molecular evidence
has supported the belief that the family radiated quickly and
suddenly, which, as a result, has caused a lack of consensus in
the scientific community about the evolution of the family
and its subfamilies. One relationship to be addressed in
murine systematics is the difference between rats and mice.
In general, animals that have a body length of less than 5.1–5.9
in (13–15 cm) are called mice, and rats are those that are
larger. Still, rats and mice diverged about 12 mya, and scien-
tists believe that murines evolved from rodents in Eurasia.

Physical characteristics A Natal multimammate mouse (Mastomys natalensis) perched on a
rock. (Photo by Rudi van Aarde. Reproduced by permission.)
The smallest murines, like the African native mice, only
reach 1.9 in (5 cm), while the largest can grow significantly 249
bigger. The greater bandicoot rats (Bandicota), for example,
can have a body length of 14.7 in (36 cm) and can weigh up
to 3.3 lb (1.5 kg). In some cases, their tails are semi-prehen-
sile and assist in climbing, and can either be scaly or slightly

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Subfamily: Rats, mice, and relatives III Vol. 16: Mammals V

The Australian jumping mouse (Notomys alexis) is the most common A long-tailed field mouse (Apodemus sylvaticus) eating a seed. (Photo
of all hopping mice. (Photo by Tom McHugh/Photo Researchers, Inc. by Stephen Dalton/Photo Researchers, Inc. Reproduced by permission.)
Reproduced by permission.)

furred. They can have opposable thumb knobs, and their bod-
ies are adapted for climbing (strong feet and semi-prehensile
tails), jumping (long hind feet), or swimming (using their tails
as rudders). They have, in general, 16 teeth (I1/0 C0/0 P0-
3/1 M0/0-3), and their rooted molars are either laminate or
cuspidate. Females have 4–24 nipples.

Distribution

The murine rodents are endemic to the Old World, in-
cluding Eurasia, Africa, and Australiasia, but human inter-
vention has spread many species throughout the Americas and
across the world. Some murine rodents have even established
populations in Antarctica.

Habitat The zebra mouse (Lemniscomys barbarus) gets its name from the
stripes on its back. (Photo by S. R. Maglione/Photo Researchers, Inc.
The animals can live in a variety of habitats, from arid Reproduced by permission.)
deserts to the jungles of the Indo-Pacific. Many of the ro-
dents have become commensal with humans and are known Grzimek’s Animal Life Encyclopedia
to be pests. Murines live in nests or burrows, either in trees,
on the ground, or in and around houses. Certain murine ro-
dents, like the brown rat, are known to live in burrows, which
has led animal biologists to study them in mazes—which
simulate their natural habitat—in order to understand how

250

Vol. 16: Mammals V Subfamily: Rats, mice, and relatives III

A house mouse (Mus musculus) carrying its newborn offspring. (Photo When threatened, the Egyptian spiny mouse (Acomys cahirinus) ex-
by Kim Taylor. Bruce Coleman, Inc. Reproduced by permission.) pands its bristles to appear larger. (Photo by E. R. Degginger/Photo
Researchers, Inc. Reproduced by permission.)
they find their way and how they learn. Once put in a maze
with food at the end, brown rats will search through the
maze and make a series of errors, but eventually will run at
high speed, without deviations, directly to the end. They
also can find their way in lit and dark mazes, are not con-
fused by inclined floors, and it is speculated that they use
their whiskers to feel the walls, and even listen to the echoes
of their noises off the walls of the maze to orient themselves.
They perform better in mazes than humans, which has lead
scientists to believe that the rats have memories and minds
conditioned, from living in underground tunnels, to a sort
of navigation.

Behavior

Old World rats and mice can be social creatures. They are
known to travel in groups (hence the term “rat packs”) and
sleep together peacefully, but can be aggressive towards mem-
bers of other rat colonies and are known to form colonial ter-
ritories. Scientists have identified up to 20 pheromones that
rats use to attract mates, as well as other scents that the ani-
mals use to mark territory or objects.

Rats are also vocal creatures and emit various sounds. En-
counters between brown rats, for example, may begin with
percussive chattering, while bush rats scream and whistle at
each other.

Feeding ecology and diet A golden spiny mouse (Acomys russatus) forages among leaf litter.
(Photo by Tom McHugh/Photo Researchers, Inc. Reproduced by per-
These animals can be nocturnal or diurnal and exhibit a wide mission.)
range of foraging behavior and food preferences. Some species
feed only on nuts and berries, while other species have been 251
known to gnaw on just about anything. They often forage or

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Subfamily: Rats, mice, and relatives III Vol. 16: Mammals V

The plains mouse (Pseudomys australis) is endemic to Australia.
(Photo by Tom McHugh/Photo Researchers, Inc. Reproduced by per-
mission.)

hunt in packs, and certain species are known to be able to catch A four-striped grass mouse (Rhabdomys pumilio) drinking from a small
birds. Aquatic species hunt fish. pool of water. (Photo by Rudi van Aarde. Reproduced by permission.)

Reproductive biology to flee from danger without making multiple trips to carry
the pups to safety. When conditions are optimal, they gener-
These animals are some of the most successful rodents in ally are able to mate year-round.
the world, in part because they reproduce frequently. Murid
rodent pups, the murines included, are usually born naked Conservation status
and blind. For the most part, their eyes open and they grow
hair within a week or two, and they are weaned shortly there- The murine rats are one of the most hardy mammalian
after. A common behavior among these rodents is that the species. They reproduce often and in great numbers and are
mothers carry their young on their nipples, which allows them highly adaptable to many environments. However, there are a

A house mouse (Mus musculus) nursing young. (Photo by Tom A western chestnut mouse (Pseudomys nanus) foraging on the ground
McHugh/Photo Researchers, Inc. Reproduced by permission.) in northern Australia. (Photo by Tom McHugh/Photo Researchers, Inc.
Reproduced by permission.)
252
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few species that are in need of conservation action if they are
to survive. Generalist species such as the black rat and brown
rat are not imperiled, but certain rats, especially those endemic
to island ecosystems, have faced habitat destruction by man and
animals. A total of 18 species are on the verge of extinction and
are classified as Critically Endangered by the IUCN.

A brown rat (Rattus norvegicus) contemplates a swim to shore. (Photo Significance to humans
by Kim Taylor. Bruce Coleman, Inc. Reproduced by permission.)
Old World rats have a long history with humans. Some
are seen as cuddly pets, like the spiny rats (genus Echimys),
while others are considered pests that eat stored food and are
indirectly responsible for killing millions of people by spread-
ing the black plague, typhus, and other maladies. However,
these pestilent creatures have become invaluable to humans:
the common lab rats and mice are descendents of the murines.
These animals have been, and will continue to be, essential
research animals, and many of the major discoveries in med-
ical psychological and research are a direct result of the
murines and their healthy ability to reproduce.

Grzimek’s Animal Life Encyclopedia 253

1 2
3
4
6 5

7

89

1. Harvest mouse (Micromys minutus); 2. House mouse (Mus musculus); 3. Creek rat (Pelomys fallax); 4. Egyptian spiny mouse (Acomys cahir-
inus); 5. Black rat (Rattus rattus); 6. Greater stick-nest rat (Leporillus conditor); 7. Australian jumping mouse (Notomys alexis); 8. Brown rat (Rat-
tus norvegicus); 9. Tree rat (Thallomys paedulcus). (Illustration by Bruce Worden)

254 Grzimek’s Animal Life Encyclopedia

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Species accounts

House mouse large appliances or inside of walls in human homes. Some
house mice live temporarily in grain fields, which they mi-
Mus musculus grate into, breed, feed, and leave when the field is plowed;
in 1926–1927, house mice nearly took over the fields of
TAXONOMY California’s Central Valley, living in them in a density of
202,000 mice per 2.5 acres (1 ha). Sometimes, they eat ani-
Mus musculus Linnaeus, 1758, Uppsala, Sweden. mal and plant pests in the fields, but they inevitably wind up
in barns and silos where they tend to contaminate food. In
OTHER COMMON NAMES general, the house mouse does not stray far from cover, with
the best habitat offering copious amounts of food, water, and
English: Mouse; French: Souris domestique; German: Haus- places to hide. Their home ranges vary, from 120 ft (36.5 m)
maus; Spanish: Ratón común. for some indoor mice to more than 2 mi (3.2 km) for certain
ones outside.
PHYSICAL CHARACTERISTICS
BEHAVIOR
Body length 5.1–9 in (13–20 cm); tail 2.3–3.9 in (6–10 cm);
weight 0.6–0.8 oz (18–23 g). A typical, stereotypical mouse, with A social species, it lives in groups with others of its kind, and
grayish brown hair on its top, relatively big ears, and a dusky, aggressive males have hierarchical ranks and tend to dominate
scaly, nearly hairless tail; the fur on its bottom is only slightly colonies. Each group lives in a territory bound by scent mark-
lighter than the fur on its top, and it has ungrooved incisors. ers, and animals within the colony have their own nests. They
will groom each other and display aggressive and submissive
DISTRIBUTION postures common in the species.

Mice spread to Europe from Asia and appeared in the sixteenth FEEDING ECOLOGY AND DIET
century in the New World on the ships of explorers. In the
seventeenth century, they appeared in northern North America Eat up to 10% of their body weight daily, and feed up to 20
and have proliferated since due to high reproductive capacity. times each day. They consume grains, fruits, vegetables, meat,
House mouse subspecies can be found across the world. insects, and have been known to eat glue, paste, and even soap.
If they eat moist food or a seed diet of 12% protein, they can
HABITAT live without water. The house mouse has been known to feed
on caterpillars, flightless moths, and earthworms.
Underground burrows, which some subspecies equip with
storage rooms. Each mouse will make its own nest, but will
share burrows with other individuals in the colony. Many
house mice are co-habitants with humans, living beneath

Mus musculus 255
Micromys minutus
Pelomys fallax

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REPRODUCTIVE BIOLOGY Rattus rattus
Rattus norvegicus
Polygynous. They reproduce copiously, and a biological con-
traceptive keeps their populations in check: females’ ovaries be-
come inoperative and the animals become infertile. They breed
throughout the year, with females giving birth to litters of
3–12 offspring about 5–10 times annually. Gestation is about
three weeks. When the young arrive, they are hairless and
their eyes are closed. Young are weaned by 21 days, they begin
to reproduce in their second month of life, and they can live,
depending on predation, to be six years old. Most wild mice
live about a year, while those in captivity generally live about
two years.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS

Over the centuries, they have spread disease and have been
used by scientists to help cure disease. The albino lab mouse,
the icon of scientific lab research, was bred from the house
mouse and has been used in everything from cancer studies to
stem cell research. At one point, cooked mouse was a folk rem-
edy for flu-like symptoms, and house mice were considered a
helper for conditions like baldness and constipation. They also
carry a variety of germs and viruses that are dangerous to hu-
mans, including tularemia, bubonic plague, spotted fever, ty-
phus, and Salmonella. ◆

Black rat BEHAVIOR

Rattus rattus These mostly nocturnal rats have used their climbing skills to
their advantage, by traveling along power lines and cables to
TAXONOMY spread from house to house. They are highly social creatures,
which travel in packs, sleep in piles, and when they meet, they
Rattus rattus (Linnaeus, 1758), Uppsala, Sweden. crawl beneath one another. They also can be territorial and
display various postures similar to other animals in the genus,
OTHER COMMON NAMES including the threat posture, a hunched, hair-bristled pose that
aggressive individuals assume to display animosity.
English: House rat, ship rat; French: Rat noir, rat commun;
German: Hausratte; Spanish: Rata de los techos, rata común. FEEDING ECOLOGY AND DIET

PHYSICAL CHARACTERISTICS Primarily vegetarians, feeding on fruit and seeds, but will eat
insects and other invertebrates if necessary.
Body length 6.3–8.6 in (16–22 cm); tail 6.7–9.8 in (17–25 cm);
weight (70–300 g). Its tail is always longer than its relatively REPRODUCTIVE BIOLOGY
slender body, and it has very large ears. Several subspecies ex-
ist, with various colorings: one has black fur on the top and Polygamous. Breed year-round in conducive habitats, produc-
gray fur on the bottom of the animal; one is agouti above and ing up to five litters per year. The females, which have 12 nip-
white below; and one is agouti above and slate below. The ani- ples, give birth to litters consisting of between 6–12 young,
mal occasionally has a white spot on its chest. with the average litter size being eight. Young open their eyes
at 15 days of age.
DISTRIBUTION
CONSERVATION STATUS
Has spread throughout the world, though it is likely native to
peninsular India. Not threatened.

HABITAT SIGNIFICANCE TO HUMANS

Found around the world because they tended to become stow- Have been closely tied with humans for thousands of years,
aways on ships, it is believed that more than 90% of rats on and are vermin-infested creatures responsible for spreading
ships were black rats. They have been found in fruit planta- various diseases to humans, including the bubonic plague that
tions, palm trees, or bushes, either in conical nests or burrows. swept Europe in the fourteenth century and various other eras.
Black rats in the modern era tend to inhabit the upper stories The rats harbor fleas, which, after biting the rat, can transfer
of wooden buildings, leading some to speculate that the ob- the bacteria responsible for the plague to humans. Black rats,
served decline in parts of Europe may have to do with the especially those in tropical climates, still spread the bubonic
gradual disappearance of wooden buildings. But they are a plague. The animals are known to strip the bark off of trees
hardy species, and now take refuge in sewers or cellars or even and they tend to infiltrate food caches and eat anything people
in trees in parts of Europe. have tried to store, including grains, seeds, cereals, and fruits.
The main predator of the black rat is the house cat. ◆
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Tree rat way back up the tree to home. Navigation is aided by scent
markings, which they lay on branches. They are expert
Thallomys paedulcus climbers and live in communities, usually in some sort of fam-
ily arrangement, with a pair of adults and their offspring and
TAXONOMY other descendents.

Mus paedulcus (Sundevall, 1846), interior of Kaffirland, South FEEDING ECOLOGY AND DIET
Africa.
Forage in their acacia trees, and are nocturnal. They eat acacia
OTHER COMMON NAMES seeds and leaflets, but if necessary will eat insects and meat.
They are able to survive without water.
English: Acacia rat.
REPRODUCTIVE BIOLOGY
PHYSICAL CHARACTERISTICS
Does not breed during the African winter, from April–July,
Body length 4.7–6.4 in (12–16.3 cm); tail 5.1–8.2 in (13–21 cm); which coincides with the lack of water during that time. When
weight 2.2–3.5 oz (63–100 g). Has long fur that ranges from the rainy season hits, the females will produce litters of 2–5
soft to coarse. Its coloring ranges from yellowish gray to gray young, however, and can breed about every 3.5 months. Ob-
to fawn on its upper parts, it has a brown tail, grayish or white served climbing trees with their young attached to their nipples.
feet and hands, red-tinted, nearly hairless ears, and a white
belly. As a rule, tree rats have tails roughly 140% the length of CONSERVATION STATUS
their bodies. They have hind feet with strong claws and a well-
developed fifth digit, which enables it to climb trees well. Not threatened.

DISTRIBUTION SIGNIFICANCE TO HUMANS

Found in Africa, between western Somalia, southern Ethiopia, An unsuitable lab rat because it does not breed well, and it is
Angola, and South Africa. capable of spreading plague and other diseases. It is often in-
fested with the stick tight flea (Echidnophaga gallinacea) as well
HABITAT as Xemonpsylla brasiliensis. It also harbors ticks and mites. ◆

Also known as the acacia rat, it makes its home in the acacia Brown rat
tree. It sometimes builds messy nests from twigs and grass in
forks or in branches, and the nests are very obvious during Rattus norvegicus
winter, when the trees lose their leaves. On occasion, however,
it will live in holes, beneath loose bark, and inside of hollow TAXONOMY
trunks. It uses the plant’s thorns as protection from predators
and can sometimes be found up to 13 ft (4 m) aboveground. Rattus norvegicus (Berkenhout, 1769), Great Britain.

BEHAVIOR OTHER COMMON NAMES

Shy animals, and will rarely leave their shelters. They are French: Rat d’égout, surmulot; German: Wanderratte; Spanish:
known to weather major storms in their nests, even during Rata noruega.
floods. Sometimes, however, they will be forced to make their
PHYSICAL CHARACTERISTICS
Acomys cahirinus
Thallomys paedulcus Body length 8.6–10.2 in (22–26 cm); tail 7–8.6 in (18–22cm);
weigh 7–14 oz (200–400 g); can reach 1.1 lb (0.5 kg) on rare
Grzimek’s Animal Life Encyclopedia occasions. Different than the black rat, in that the brown rat
grows larger, has a thicker build, shorter ears and tail, and
coarser fur. It is reddish brown to grayish brown on the back
and often has darker sides. Fur on its belly is a light slate.

DISTRIBUTION

Believed to have originated in the northern regions of Asia,
perhaps in China or Mongolia, and spread westward. It
reached Western Europe in 1716 via a ship docking in Copen-
hagen; hit France in 1735, and then the shores of America in
1755, it spread to England by 1750. Ships and ocean vessels
have spread the rodents to nearly all of the world’s seaports.

HABITAT

Lives just about anywhere, but it does not fare well in hotter
climates. It is well adapted for the colder climes, and the
species has actually inhabited a whaling station in Antarctica. It
lives in close proximity to humans, often found anywhere from
burrows and cavities to sewers and cellars. In homes, brown
rats, which are poor climbers, are at ground level. Although
the species is not aquatic, it can swim well and has been spot-
ted in rivers or ocean waters.

BEHAVIOR

Social animals that live and hunt in groups with close familial
relationships, although they do allow non-related animals in on

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occasion. They can form groups as large as 200 animals usually builds nests, suspended between grass stems, about 3.2 ft (1 m)
with a dominant male overseeing the social order. Dominance aboveground. The nests, which can take two days to build, are
hierarchies are determined by size and weight rather than age. made from woven leaves, with the inner layer being finely
shredded to provide a soft spot for young. The animals also
FEEDING ECOLOGY AND DIET nest in holes or, in some circumstances, on the ground during
winter. They may also move into human structures like barns
Eats a variety of things, although it prefers meat. It can swim, to avoid the cold.
dive, and catch fish. In the 1940s, a pack of 15,000 brown rats
decimated the bird population of a sanctuary on the island of BEHAVIOR
Nooderoog, eating eggs and catching seagulls, ducks, passer-
ines, and other species. They have also been known to eat Nocturnal. The animals live in crowded conditions, but are not
mice, chickens, ducks, and geese, and will gnaw on lambs and as social as black or brown rats. Captive males have been
piglets. Rat packs have ganged up to kill cats and dogs that known to fight each other, and males and females only come
have been deployed to keep their populations in check. They together to build nests and to mate. Females chatter to attract
have been known to feed on elephants, invalids, and newborn mates and squeal during aggressive outbursts.
babies. They have also been described as cannibalistic. It will
take its catch back to its den for feasting, and can live without FEEDING ECOLOGY AND DIET
water as long as it consumes sufficiently moist food.
Forages in the grass fields primarily before dawn and just after
REPRODUCTIVE BIOLOGY dusk. It feeds on seeds and vegetables, but does on occasion
take insects and eggs of small birds. Their unique climbing
They will breed throughout the year, although they peak in adaptations, like their semi-prehensile tail and their feet, allow
the spring and fall. When females go into heat, which lasts for them to climb through grass fields and counterbalance them-
six hours, a collection of males will mate with her. Each female selves as they move about.
will produce between 2–12 litters each year, with each litter
consisting of 6–12—and as many as 22—young. The pups are REPRODUCTIVE BIOLOGY
born blind and pink, they open their eyes after about two
weeks, and they leave the nest after three weeks. In a pack, the Polygamous. Females reproduce during the warmer months,
females give birth to their pups in the same room and assist from May–September, and they are capable of giving birth sev-
each other in raising their young. The young are able to breed eral times in succession. Gestation time is about 2.5 weeks.
after 90 days. In optimal conditions, the animals are capable of Each litter ranges from one to 13 pups, with an average of five.
producing up to 800 offspring per year, but this number is They are blind and naked at birth, but within 10 days can see
considerably lower in the wild. and have fur. They are weaned at two weeks and start to repro-
duce at one month of age. They are capable of living to nearly
CONSERVATION STATUS five years in captivity, but rarely live longer than six months in
the wild.
Not threatened.
CONSERVATION STATUS
SIGNIFICANCE TO HUMANS
Not threatened, but certain populations near farm machinery
Best known as carriers of the bubonic plague, and for centuries are in decline due to habitat loss.
have eaten and contaminated human food. A descendent, the
white albino lab rat, has proven invaluable to scientific research SIGNIFICANCE TO HUMANS
and discoveries in human health research. ◆
No major significance. ◆

Harvest mouse Creek rat

Micromys minutus Pelomys fallax

TAXONOMY TAXONOMY

Micromys minutus (Pallas, 1771), Ulyanovsk, Russia. Pelomys fallax (Peters, 1852), Zambezi River, Mozambique.

OTHER COMMON NAMES OTHER COMMON NAMES

English: Old World harvest mouse; French: Souris des moissons; English: Swamp rat, groove-toothed swamp rat.
German: Eurasiatische zwergmaus; Spanish: Ratón espiguero.
PHYSICAL CHARACTERISTICS
PHYSICAL CHARACTERISTICS
Body length 3.9–8.2 in (10–21 cm); tail 3.9–7 in (10–18 cm);
One of the smallest rodents: length 2.1–2.9 in (5.5–7.5 cm); tail weight 3.9–7 oz (100–170 g). The animal has rusty brown fur
1.9–2.7 in (5–7 cm); weight 0.17–0.24 oz (5–7 g). Brownish on top and a dirty white on bottom; the fur is rough, but not
color with lighter tint on top, its fur grows longer in the win- spiny. There is also a variable dorsal line that runs to the tail
ter, and it has small ears, broad feet, and no hair on the top of that is especially prominent in young animals. The tail is
the end of its tail, which is semi-prehensile. Its feet are adapted haired, with white below and black on top, and its length varies
to a climbing lifestyle. with populations. It has grooved upper incisors, which is un-
usual in the murines.
DISTRIBUTION
DISTRIBUTION
Generally found where there is high grass, specifically in
northern Eurasia. It is also distributed throughout Siberia, Ko- Distributed throughout southern Africa, in northern Mozam-
rea, China, Great Britain, Japan, and Taiwan. bique, northwestern Zimbabwe, northern Botswana, Zambia,
the Congo, Malawi, Tanzania, southwestern Uganda, and
HABITAT southern Kenya.

Lives in high grass, in areas such as pastures, grain fields, and HABITAT
rice fields. It can also be found in bamboo thickets. The animal
Inhabit streams, rivers, riverbanks, and swamps, or anywhere
258 there is substantial amounts of water and vegetation. They can

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Vol. 16: Mammals V Subfamily: Rats, mice, and relatives III

also live in grasslands, provided these areas border swamps or also feed on snails as well as plant materials, including grains
rivers. and grasses. Some species have begun to live in close proximity
to humans, and are known to feed on grains and other foods
BEHAVIOR that have been stored away.

Generally diurnal and aquatic, it is an excellent swimmer and is REPRODUCTIVE BIOLOGY
said to be difficult to trap. It is often found sunbathing on
matted reeds and grasses. Build a rudimentary nest in which to give birth. The gestation
period is 5–6 weeks, or about two weeks longer than the
FEEDING ECOLOGY AND DIET mouse norm, and small litters of 1–5 young are born. They are
capable of breeding again almost immediately after birth, and
Vegetarian, and it eats reeds, grasses, seeds, and other plants they have been known to string together over 12 litters in suc-
and plant material. cession. What sets the spiny mouse apart from other mice is
that the young are well developed at birth. They are born with
REPRODUCTIVE BIOLOGY hair that, although thin, is enough to allow the pups to ther-
moregulate, which means the mother does not need to give
Little is known, other than no predictable breeding season ex- them much body warmth. Further, their eyes are either open
ists. The animals tend to reproduce in the warmer months, at birth or within a day or two of birth. By day three, the
from August–April, and litter sizes ranger from 2–4 young. It is young are exploring. Due to the social nature of the creatures,
not determined if they live above or below ground: some be- females help each other during the birthing process. In func-
lieve they make shallow burrows, since their bodies have tion, all the females in a group help raise the young.
turned up in tilled fields, while others have surveyed habitat ar-
eas and have found no holes that could be burrows. CONSERVATION STATUS

CONSERVATION STATUS Not threatened, although Acomys cilicicus is listed as Critically
Endangered, while Acomys minous is Vulnerable.
Not threatened.
SIGNIFICANCE TO HUMANS
SIGNIFICANCE TO HUMANS
Although the animals are known to spread typhus, they have
Not considered a pest and is eaten by tribes in Angola. ◆ recently received significant attention as a worthwhile pet. Ap-
parently, people enjoy keeping the animals because their urine
Egyptian spiny mouse is relatively devoid of odor, and they are docile. The spiny
mouse pet trade appeared in the mid 1980s. ◆
Acomys cahirinus
Greater stick-nest rat
TAXONOMY
Leporillus conditor
Mus cahirinus (Desmarest, 1819), Cairo, Egypt.
TAXONOMY
OTHER COMMON NAMES
Leporillus conditor (Stuart, 1848), New South Wales, Australia.
English: Spiny mouse; French: Rats épineux; German:
Stachelmäuse; Spanish: Ratón espinoso. OTHER COMMON NAMES

PHYSICAL CHARACTERISTICS English: Stick nest rat, Australian stick nest rat, house-building
rat, Franklin Island stick-nest rat, Franklin Island house-build-
Body length 2.7–6.7 in (7–17 cm); tail 1.9–4.7 in (5–12 cm); ing rat; French: Léporilles; German: Zweignestratten.
weight 1–2.4 oz (30–70 g). The defining feature is the gray-
brown to sandy spiny hairs covering its back. The large-eared PHYSICAL CHARACTERISTICS
animal has a gray to white belly and a scaly, hairless tail.
Body length 6.7–10.2 in (17–26 cm); tail 5.7–7 in (14.5–18 cm);
DISTRIBUTION weight (180–450 g). It has large eyes and large ears, which are
round and dark. Its tail has hair, with longer bristles at the
Distributed through Africa and the Middle East. The Egyptian end. Covered in soft fur that is light gray or white below and
spiny mouse is widely distributed, but it was first discovered in yellowish brown or gray on top.
Egypt.
DISTRIBUTION
HABITAT
Originally distributed throughout southern Australia, from the
Live in arid and semi-arid environments like deserts and savan- Shark Bay vicinity to western New South Wales. It was also
nahs. They live in and around rocks and can be found in bur- found in Franklin Island and northwestern Victoria. Currently,
rows, which they presumably do not dig themselves, and have due to declining numbers, it is found naturally occurring only
been found in trees even though they are terrestrial. They tend on the East and West Franklin Islands. Captive-bred individu-
to avoid altitudes above 4,920 ft (1,500 m), and in some places, als have been successfully reintroduced on other islands, as well
particularly in Egypt, the animals live with and off of humans. as only a few fenced-in areas in the original distribution range.

BEHAVIOR HABITAT

Different spiny mice species (there are eight) feed at different Inhabit arid regions with little or no fresh water. They use re-
times and thus avoid competing with each other over the gional twigs and shrubs to build enormous nests that can reach
amount of insects they eat. Still, they are also known to be rel- over a 3.2 ft (1 m) high.
atively social, and live in small groups with a dominant male
who, when challenged, will fight. The animals are excellent BEHAVIOR
jumpers and fairly active. Humans do keep them as pets.
The nocturnal rodents are sometimes known to build giant,
FEEDING ECOLOGY AND DIET towering nests called “wurlies” from sticks, twigs, and plant

Takes arthropods; certain species forage at different times in 259
order to reduce interspecies competition. However, the animals

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Subfamily: Rats, mice, and relatives III Vol. 16: Mammals V

habitat. Scientists have been trying to repopulate various off-
shore Australian islands with the rats after having eradicated
feral cats and other pests that could prey on the animals. Over
the past few years, a successful breeding program in captivity
has produced a large number of rats used to repopulate Aus-
tralia, and the total greater stick-nest rat population has in-
creased fivefold to over 5,000 individuals. ◆

Notomys alexis Australian jumping mouse

Leporillus conditor Notomys alexis

stalks. They usually use a preexisting shrub, and sometimes, TAXONOMY
large rocks, to scaffold the nest; they proceed to weave sticks
around the framing shrub. They occasionally incorporate Notomys alexis (Thomas, 1922), Northern Territory, Australia.
stones into the nest, which serve to anchor it against winds,
and they line the center with grasses. Up to 20 rats can live OTHER COMMON NAMES
in the largest nests, which are filled with tunnels leading from
the nest center to its outside. Younger generations inherit the English: Australian hopping mouse, jerboa mouse; French:
nests and the task of tending to them. In fact, the nests have Souris sauteuses d’Australie; German: Australische Hüpfmäuse;
been shared with bandicoots, snakes, penguins, and shearwa- Spanish: Ratón saltador.
ters. Further, they are known to be docile and do not bite
humans when handled. However, the social animals live in PHYSICAL CHARACTERISTICS
groups and display aggression towards unknown greater stick-
nest rats. Body length 3.9–5.9 in (10–15 cm); tail 3.5–8.2 in (9–21 cm);
weight 0.7–1.7 oz (20–50 g). Their upper coloring is light sandy
FEEDING ECOLOGY AND DIET brown to gray. Their bellies are white to light gray. They have
long tails and large ears, but their distinguishing feature is the
Completely vegetarian, feeding on leaves and fruits and succu- narrow, large hind feet that enable them to effortlessly jump
lents for hydration. higher than 3.2 ft (1 m), and relatively small forefeet. Their tails
are long and finely coated and, like the rest of the genus, have
REPRODUCTIVE BIOLOGY sebaceous glands, which are utilized for territorial marking.

When conditions are optimal, the animals can breed anytime DISTRIBUTION
of the year. Gestation lasts for about six weeks, litters consist
of only several young weaned after a few months, and they re- Endemic to and spread throughout central Australia’s deserts
produce only two or three times annually, making their repro- arid landscapes.
ductive rates far less than more successful murine rodents like
black rats. HABITAT

CONSERVATION STATUS Live in dunes and grasslands and dig burrows that can vary in
complexity.
Recently upgraded from Endangered to Vulnerable due to re-
covery efforts; its relative, the lesser stick-nest rat, is assumed BEHAVIOR
to be Extinct.
Nocturnal social creatures, they involve themselves in groom-
SIGNIFICANCE TO HUMANS ing, huddling, walking over each other, crawling under each
other, and sleeping together. When they fight, they not only
None, but theirs numbers have disappeared in part because of rush at each other and punch each other with their fore legs,
humans. Introduced animals like sheep have overgrazed and but they also leap at each other. The hopping mice generally
subsequently destroyed much of their preferred shrubland walk on all fours, but in cases of haste and aggression will leap
with their hind legs. They also live in groups with a high maxi-
260 mum density.

FEEDING ECOLOGY AND DIET

Eat berries and other vegetation, but they can live without wa-
ter provided they receive sufficient hydration from their regular
diet. They have extremely concentrated urine and avoid dehy-
dration by staying underground during periods of intense heat.

REPRODUCTIVE BIOLOGY

A month-long gestation period leads to a litter of about three
pups. They are born naked and blind, but open their eyes by
week three and are weaned after five weeks and are ready to
reproduce at three months. Females carry their young by their
nipples. Their reproductive rates vary widely, depending on
ecological conditions.

CONSERVATION STATUS

The dusky hopping mouse, N. fuscus, is listed as Vulnerable.

SIGNIFICANCE TO HUMANS

There is no major significance to humans, but they have be-
come popular pets. ◆

Grzimek’s Animal Life Encyclopedia

Vol. 16: Mammals V Subfamily: Rats, mice, and relatives III

Common name / Physical Habitat and Distribution Conservation
Scientific name/ characteristics behavior Diet status
Other common names

Golden spiny mouse Light golden brown, underparts are Arid regions consisting of Eastern Egypt, Sinai, Animal matter but also Not threatened
Acomys russatus white. Pelage is bristly, the ends of the includes snails, insects,
German: Goldene Stachelmaus spines are black or gray. White patch deserts and savannas Jordan, Israel, and seeds, and other plant
below each eye and ear. Head and body material.
length 2.7–5.9 in (7–15 cm), tail length dominated by rocky crevices. Saudi Arabia.
1.5–5.1 in (4–13 cm), weight 0.5–2.8 oz
(15–80 g). Breeds throughout the year.

Cyprus spiny mouse Predominantly golden brown. Long, Deserts, savanna, and dry Cyprus. Mainly snails and insects. Data Deficient
Acomys nesiotes drawn-out pointed face that tapers out steppes with stony areas.
German: Zypern-Stachelmaus into a pointed nose. High-standing funnel Build nests; good runners
ears. Head and body length 3.5–5.1 in and climbers.
(9–13 cm), tail length 3.5–4.7 in (9–
12 cm).

Striped field mouse Yellow-brown with black, mid-dorsal Grassy fields, cultivated Central Europe to Lake Roots, grains, seeds, Not threatened
Apodemus agrarius stripe. Head and body length 3.7–4.5 in areas, paddies, woodlands, Baikal, south to Thrace, berries, nuts, and insects.
German: Brandmaus (9.4–11.6 cm), tail length 0.7–8 in (1.9– and forests. Breeding season Caucasus, and Tien
2.1 cm). throughout the year. Females Shan Mountains; Amur
can produce up to six litters River through Korea to
per year, each of up to six eastern Xizang and
young. eastern Yunnan,
western Sichuan, Fujiau,
and Taiwan, China; and
Quelpart Island, Korea.

Long-tailed field mouse Grayish buff, grayish brown, brown with Grassy fields, cultivated Europe north to Roots, grains, seeds, Not threatened
Apodemus sylvaticus yellow or red, mixed with pale sand color. areas, woodlands and
German: Waldmaus; Spanish: Underparts are white or light gray. Feet forests. Produces up to four Scandinavia and east to berries, nuts, grasses,
Ratolí de rostoll are white, tail not prehensile. Head and litters a year, each with four
body length 2.3–5.9 in (6–15 cm), tail to seven young. Nocturnal. northwestern Ukraine grain kernels, fruits, and
length 2.7–5.7 in (7–14.5 cm).
and northern Belarus, insects.

and on many islands,

as well as mountains of

northern Africa from

Atlas Mountains in

Morocco east across

Algiers to Tunisia.

African grass rat Stout body, short legs. Coloration ranges Savanna grasslands. Five to Most of Africa. Grains, seeds, grass Not threatened
Arvicanthis niloticus from buff to olive brown to dark gray- six young per litter.
brown. May have dorsal stripe. Under Gregarious, live in burrow shoots, as well as insects
parts are lighter. Weight 1.7–4.2 oz (50– systems.
120 g). and fruits.

Golden-bellied water rat Webbed, broad front and hind feet. Blunt Found near permanent fresh Australia, Tasmania, Crustaceans, mollusks, Not threatened
Hydromys chrysogaster muzzle with whiskers, flat head with water. Dependent on water and New Guinea. fish, ducks, poultry, frogs,
German: Australische small ears and eyes. Thick, white-tipped for food. Breeds in spring turtles, bats, house mice,
Schwimmratte tail. and summer, lives alone or and aquatic insects.
in pairs in burrow system.
Diurnal, sedentary, and
generally solitary.

Short-tailed bandicoot rat Dull brown or grayish brown on back, Moist areas or along streams Egypt to Sinkiang and Leaves and roots of lawn Not threatened
Nesokia indica underparts are light gray. Pelage ranges and canals, as well as northern India. grass.
from dense and coarse to long and deserts, steppes, cultivated
Dusky hopping mouse smooth. Head and body length 5.5–8.4 in areas, and forests. Nocturnal
Notomys fuscus (14–21.5 cm), tail length 3.4–5 in (8.8– and fossorial. Make
French: Souris sauteuse; 12.9 cm). extensive burrows with
Spanish: Ratones saltadores several chambers. A single
de Australia rat occupies each burrow.

Long tail, large ears, and dark eyes. Sand dunes, grasslands, tree Australia. Seeds, berries, leaves, Vulnerable
green plants, and
Upperparts range from pale sandy and shrub heaths, and lightly occasionally insects.

brown to yellowish brown to ashy wooded areas. Build nests;

brown or grayish. Underparts are white. glands used for marking

Head and body length 3.5–7 in (9.1–17.7 territories and individuals.

cm), tail length 4.9–8.8 in (12.5–22.5 cm).

[continued]

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Subfamily: Rats, mice, and relatives III Vol. 16: Mammals V

Common name / Physical Habitat and Distribution Conservation
Scientific name/ characteristics behavior Diet status
Other common names

Long-tailed mouse Grayish brown above, underparts are Areas with high annual Australia and Tasmania. Monocotyledons, Not threatened
Pseudomys higginsi white. Bicolor tail, tipped with white. rainfall, such as rainforests, subterranean fungi, fruits
Nostril is pink and naked. Head and body wet sclerophyll forests, wet of shrubs, and
length 5 in (13 cm), weight 2.1–2.5 oz scrub, and eucalyptus scrub. invertebrates.
(60–70 g). Breeding season from
November to April. One to
two litters in a season, each
with a litter size of three to
four offspring. Nocturnal,
motile, and sedentary.

False water rat Long, flat head with small eyes and Coastal swamps with Northern Territory and Small crustaceans such Vulnerable
mangrove forest. Nocturnal. Melville Island off the as crabs, marine
Xeromys myoides short, rounded ears. Coloration is dark Litter size is small, two coast of Northern polyclads, marine
offspring. Little is known of Territory, Australia. pulmonates, shellfish,
French: Faux rat d’eau; Spanish: gray, white underside. Coat is water reproductive patterns. and worms.

Rata bastarda de agua resistant. Tail is scaled. Head and body

length 4.5–10.6 in (11.5–27 cm), tail

length 3.3–3.9 in (8.5–10 cm), weight

1.4–2.1 oz (40–60 g).

Resources The Department for Environment and Heritage of Southern
Australia. GPO Box 1047, Adelaide, South Australia 5001
Books Australia. Phone: (8) 8204-9000. Web site: <http://www
Alderton, David. Rodents of the World. New York: Facts on File, .environment.sa.gov.au/>

1996. The Department of Conservation and Land Management for
Western Australia. Hackett Drive, Crawley, Western
Barnett, S. Anthony. The Story of Rats. Crows Nest, Australia: Australia 6009 Australia. Phone: (8) 9442-0300. Fax: (8)
Allen & Unwin, 2001. 9386-1578. Web site: <http://www.calm.wa.gov.au/>

Corbett, G. B., and F. Hill. A World List of Mammalian Species. IUCN—The World Conservation Union. Rue Mauverney 28,
New York: Facts on File, 1986. Gland, 1196 Switzerland. Phone: +41 (22) 999 0000. Fax:
+41 (22) 999 0002. E-mail: [email protected] Web site:
De Graff, G. “Creek Rats.” In Rodents of Southern Africa. <http://www.iucn.org>
Woburn, MA: Durban, 1981.
The National Wildlife Federation. 1045 Sansome St., Suite
———. “Tree Rats.” In Rodents of Southern Africa. Woburn, 304, San Francisco, CA 94111 USA. Phone: (415) 732-7000.
MA: Durban, 1981. Fax: (415) 732-7007. Web site: <http://www.nwf.org/> and
<http://www.enature.com>
Hanzak, J. Encyclopedia of Animals. New York: St. Martin’s
Press, 1965. Other
Rodentmania, The Rodent Dictionary. [June 2003]
Nowak, R. M. Walker’s Mammals of the World. 6th ed.
Baltimore and London: Johns Hopkins University Press, <http://members.tripod.com/Nager/index.htm>.
1999.
Animal Info: Rare, Threatened and Endangered Mammals. [June
Periodicals 2003] <http://www.animalinfo.org/>.
Flaming, P. A., and S. W. Nicolson. “Opportunistic Breeding
The Animal Diversity Web. [June 2003]
in the Cape Spiny Mouse Acomys subspinosus.” African <http://animaldiversity.ummz.umich.edu/>.
Zoology 37, no. 1 (2002): 101–105.
Smithsonian Institute, Murine Species List. [June 2003] <gopher://
Le Roux, V., J. L. Chapuis, Y. Frenot, and P. Veron. “Diet of nmnhgoph.si.edu:70/0R144788-165041-/.docs/mammals_
the House Mouse (Mus musculus) on Guillou Island, data/list>.
Kerguelen Archipelago, Subantarctic.” Polar Biology 25
(2002): 49–57. The House Mouse. [June 2003]
<http://www.death-valley.us/article41.html>.
Kronfeld-Schor, N., and T. Dayan. “The Dietary Basis for
Temporal Partitioning: Food Habits of Coexisting Acomys Molecular Systematics (for Rodents). [June 2003]
Species.” Oecologia 121, no. 1 (1999): 123–128. <http://cgb.utmem.edu/faculty/Adkins/>.

Organizations Nathan S. Welton
American Zoo and Aquarium Association Behavioral Advisory

Group’s ethograms.org.
Web site: <http://www.ethograms.org>

262 Grzimek’s Animal Life Encyclopedia

᭝

Rats, mice, and relatives IV

South American rats and mice (Sigmodontinae)

Class Mammalia
Order Rodentia
Suborder Sciurognathi
Family Muridae
Subfamily Sigmodontinae

Thumbnail description
Small- to medium-sized mice and rats; in
general brownish or blackish upper pelage and
grayish or whitish underparts; tail usually thinly
haired; molars with two rows of cusps

Size
Head and body length: 2.4–11.4 in (61–290
mm); tail length 1–6.3 in (30–160 mm); weight:
0.4–18 oz (12–510 g).

Number of genera, species
71 genera; 373 species

Habitat
All habitats (e.g., dry deserts, wet tropical
forests, wetlands, savannas, steppes,
temperate woodlands, high altitude grasslands,
salt flats, scrublands) found in their distribution
range up to 17,000 ft (5,200 m) above sea
level

Conservation status Distribution
Extinct: 6 species; Critically Endangered: 8 Endemic to the New World; living forms range from Tierra del Fuego, the
species; Endangered: 24 species; Vulnerable: southernmost part of South America, up to southern United States; also distributed
23 species; Lower Risk/Near Threatened: 36 on some islands adjacent to the continent as well as in the oceanic Galápagos
species; Data Deficient: 3 species archipelago

Evolution and systematics the rice rats (Oryzomys), but the subfamily also encompasses
an enormously diverse collection of other rodents practically
Over the last several decades, the contents and limits of unknown to most people.
the subfamily Sigmodontinae have been a center of much de-
bate. However, as of 2001, an agreement has been reached in Traditionally, sigmodontine genera have been arranged
defining Sigmodontinae to only encompass the predomi- into different groups, some have been formalized as tribes in
nantly South American complex-penised mice and rats, leav- zoological classifications. Depending on the relative weight
ing out of the subfamily those predominantly North American that is given to different trenchant characters, the number and
simple-penised mice and rats (e.g., the wood rats Neotoma, the content of sigmodontine groups vary from author to author.
grasshopper mice Onychomys, and deer mice Peromyscus). Now In the early 1990s an almost universal adoption of a phyloge-
defined, the subfamily Sigmodontinae includes 71 living gen- netic approach to delimit these groups caused major recon-
era and 373 species. Remarkably, these numbers keep grow- siderations on the identity of the groups as well as on their
ing as new genera and species are being discovered and limits and contents. These studies have promoted: the recog-
identified from both field and museum based work. New sig- nition of a previously unnoted group (the abrothricines, mostly
modontines are being discovered even in areas that are pre- confined to the central and south Andes); the subsuming of
sumably well known from a mammalogical point of view. For some main groups within others (e.g., scapteromyines into
example, Oxymycterus josei was described in 2002 for the first akodontines); the corroboration of the distinction of some
time from areas near the southern coast of Uruguay. These groups (e.g., reithrodontines, wiedomyines); and called into
areas have been frequently visited by mammalogists since the question the nature of at least one group (the thomasomyines)
early nineteenth century. Sigmodontines include several fa- and the composition of most groups. As of 2003, nine main
miliar rats and mice, such as the cotton rats (Sigmodon), and sigmodontine groups are recognized (Smith and Patton, 1999).

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Subfamily: Rats, mice, and relatives IV Vol. 16: Mammals V

more abundant in late Pleistocene sediments. While, more
than a half of extant genera are also recorded as fossils (many
from Holocene beds), only seven known genera have become
extinct during geologic times. In addition, three genera pre-
sumably became extinct in historic times. The sigmodontine
nature of some North American fossils, such as Prosigmodon,
Bensonomys, and Symmetrodontomys, is questionable and de-
serves further scrutiny.

The understanding of sigmodontine evolutionary history
has proved to be a complex task. All students agree on the
fact that in spite of most sigmodontines being endemic to
South America, the immediate ancestor of the group did not
originate in South America. In other words, at some point in
history sigmodontines or their immediate ancestor invaded
South America. The basis for this agreement lies on the fact
that no potential ancestor has yet been discovered in South
America. The fossil record indicates that this invasion was as
late as Late Miocene. As of 2003, two main aspects of sig-
modontine historical biogeography remain unresolved. These
are: 1) whether the geographic origin of the stock that gave
rise to the sigmodontines was in the Old World or in Cen-
tral-North America; and 2) the geographic placement of the
basal sigmodontine radiation; in other words, how many sig-
modontine lines invaded South America? Evidence at hand
tends to indicate that the sigmodontine ancestor inhabited
Central-North America. However, the numbers of sigmod-
ontine lines that invaded South America remains to be solved.
Therefore, it is not clear if North American sigmodontine are
direct descendents of the first sigmodontines or if they rep-
resent secondary invasions to North America of lines first dif-
ferentiated in South America.

Plains harvest mice (Reithrodontomys montanus). (Photo by Stephen Physical characteristics
Dalton/Photo Researchers, Inc. Reproduced by permission.)
Although most sigmodontines are typical mice and rats,
Diversity is not evenly distributed among them. The akodon- the group exhibits several deviations from this morphotype.
tines, oryzomyines, and phyllotines account for more than
half of extant genera. The abrotrichines, the ichthyomyines, A cactus mouse (Peromyscus eremicus) in the California desert, USA.
the reithrodontines, the sigmodontines, the thomasomyines, (Photo by Anthony Mercieca/Photo Researchers, Inc. Reproduced by
and the wiedomyines are groups of one to five extant genera permission.)
each. In addition, there are several extant genera whose phy-
logenetic relationships are not clear; these genera cannot be Grzimek’s Animal Life Encyclopedia
assigned with certainty to any monophyletic group less in-
clusive than the subfamily. In formal classifications these
genera (e.g., Abrawayaomys, Delomys, Irenomys, Juliomys,
Phaenomys, Punomys, Rhagomys, Wilfredomys) are generally
considered as incertae sedis (of uncertain taxonomic position).
Phylogenetic relationships among sigmodontine main groups
or tribes are mostly unclear. The only point that appears well
corroborated is that the Sigmodontini, composed only of one
extant genera (Sigmodon), is the sister group of all remaining
sigmodontines.

Although extensive, past sigmodontine diversity is not as
great as the present (Pardiñas et al. in press). The oldest South
American known sigmodontine comes from the latest
Miocene sediments of the Argentinean province of La Pampa.
Sigmodontines are rare in early Pliocene beds and become

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Vol. 16: Mammals V Subfamily: Rats, mice, and relatives IV

A deer mouse (Peromyscus maniculatus) standing on lichen. (Photo roots. For example, Reig in 1977 nominated more than 30
by Maslowski/Photo Researchers, Inc. Reproduced by permission.) cusps, cuspules, styles, lophs, folds, and islands, in an ideal-
ized sigmodontine molar. Molar crown height seems to be re-
lated to diet. In general, sigmodontines that feed on animals,
seeds, fruits, or fungus have low-crowned molars (brachydont)
that retain complex occlusal surface. High-crowned molars
(hypsodont), which extend far above the gumline, are usually
present in those sigmodontines, as Andinomys and Reithrodon,
which feed on abrasive vegetation (e.g., grass). Usually, the
hypsodont condition is associated with a simplification of the
occlusal surface, connection of lophs on each tooth side to
form lamina, planation of the crown, and an increase in the
number of tooth roots.

With a few well recognized exceptions, sigmodontines
have complex penises. A complex penis has two lateral horns
on the cartilagenous distal baculum, making it appear as tri-
dent shaped.

Examples of these departures are the shrew mouse Blarino- Distribution
mys, the mole mouse Geoxus, the chinchilla mouse Chinchillula,
and the rabbit rat Reithrodon. Sigmodontines are small. They Sigmodontines are a New World group; currently they
range from about 0.4 to about 14.1 oz (12 to about 400 g). range from Tierra del Fuego, the southernmost part of South
The largest living form, Kunsia tomentosus, does not surpass America, north to the southern United States. They are also
11.8 in (300 mm) of head and body length. External ears vary distributed on some islands adjacent to the continent, as well
from almost absent or much reduced (e.g., the aquatic rat An- as in some oceanic islands as the Galápagos archipelago. How-
otomys and the long-clawed mole mouse Geoxus) to moder- ever, most of extant sigmodontine diversity is confined to the
ately large (e.g., the long-eared mice of the genus Phyllotis) or South American continent. In fact, 61 living genera are en-
large (e.g., the rabbit rats of the genus Reithrodon). Climbing, demic to South America and the neighboring islands such as
arboreal and scansorial species tend to have tails longer than Trinidad. Three genera: Oligoryzomys, Oryzomys, and Sig-
head and body length; tail approximately equal to combined
head and body is characteristic of the more generalized ter- The saltmarsh harvest mouse (Reithrodontomys raviventris) is active
restrial sigmodontines; while the tail of fossorial species is usu- primarily at night, but may be seen during the day. (Photo by Tom
ally less than half of head and body length. The tail is usually McHugh/Photo Researchers, Inc. Reproduced by permission.)
thinly haired, but in some sigmodontines ends in a penciled
tip (e.g., Andalgalomys). Most sigmodontines have a brownish 265
or blackish upper pelage and grayish or whitish underparts.
However, Chinchillula is noticeable in this regard; its upper
parts are buffy or grayish with black lines, the underparts are
white, and the white hips and white rump banded with black.
Sigmodontine fur may be velvety, soft, woolly, long, thick,
harsh, composed of underfur and guard hairs. Abrawayaomys,
Neacomys, and Scolomys have some hairs modified into spines.
Sigmodontine feet also show variation. In general, feet are
relatively small, but those of fossorial forms like the giant rat
Kunsia are robust and extremely long clawed; those of swim-
mers like the marsh rat Lundomys are large and webbed, and
those of climbers (e.g., Rhipidomys) are broad and strongly
grasping. Finally, the hindfoot of the arboreal mouse
Rhagomys is remarkable among sigmodontine because the fifth
toe is long, and the big toe presents a nail instead of a claw.

As in all rodents, one upper and one lower incisor (some-
times grooved) are found on each side of the jaw, and canines
and premolars are never present. After an empty space, called
diastema, following the incisor, three cheek teeth, or molars,
occur on each side. The total number of teeth is 16. The ex-
ception to this pattern is the ichthyomyine Neusticomys oy-
apocki that has two molars per upper and lower jaw. There is
a large variation in molar size, morphology, and number of

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Subfamily: Rats, mice, and relatives IV Vol. 16: Mammals V

Brush mice (Peromyscus boylii) are omnivorous. (Photo by Anthony Mer- Habitat
cieca/Photo Researchers. Reproduced by permission.)
Sigmodontines occupy almost all ecosystems found
modon inhabit areas of the three Americas. Seven genera are through their distributional range, including dry deserts, wet
distributed in Central and South America, although three of tropical forests, wetlands, savannas, steppes, temperate wood-
these, Ichthyomys, Oecomys, and Rhipidomys, have only Panama lands, high altitude grasslands, salt flats, and scrublands. Some
as their extra South American part of the range. The water species, such as Nectomys squamipes, are semiaquatic inhabi-
mouse Rheomys is the only mainland genus not present in tants of forests, and others, like Scapteromys tumidus, are semi-
South America. In addition, the living genus Nesoryzomys is aquatic inhabitants of grasslands. Notiomys edwardsii and
endemic to the Galápagos Islands. Finally, three genera that Kunsia tomentosus are largely fossorial species that live in arid
presumably became extinct in historic time: Megalomys, steppes and savanna forest, respectively. Thomasomys aureus
Megaoryzomys, and Noronhomys were endemic, respectively, to and Irenomys tarsalis are arboreal species that live in cloud for-
the Lesser Antillas, and the oceanic Galápagos and Fernando est and temperate forest, respectively.
de Noronha Islands. However, this last statement may change
since an undescribed fossil from mainland Argentina may be Some sigmodontines inhabit more than one habitat type.
assignable to Noronhomys (Pardiñas, pers. com.). For example, the rabbit rat Reithrodon auritus is found, among
others, in steppes, bunchgrass prairies, dense grasslands, beech
The past distribution of the subfamily as a whole roughly forests, and sparse shrub lands. Similarly, Azara’s field mouse
matches current distribution. Lack of fossil records from some Akodon azarae lives in several types of open environments, in-
areas (e.g., most of the Amazon basin or the highland Puna) cluding dry and humid Chaco, pampas grasslands, and agrosys-
is probably due to the lack of adequate sediment beds and/or tems. Meanwhile, other sigmodontines appear restricted to
insufficient exploratory work. However, it is worth noting that specific habitat types. For instance, the poorly known Puno-
the distributions of several genera, such as Bibimys, Kunsia, mys lemminus occurs only in the treeless Puna of Peru between
and Pseudoryzomys, have markedly shifted in a few thousand 14,600 and 17,000 ft (4,450–5,200 m) of elevation.
or even hundred years (Pardiñas, 1999).
While some sigmodontines appear to be highly sensitive
It has to be emphasized that much still remains to be to habitat destruction (e.g., Anotomys leander and Pearsonomys
learned about sigmodontine distribution, as is shown by the annectens), others appear to adapt well to human disturbed
results of field work conducted in the late twentieth and early habitats. The latter is the case of the field mouse Akodon
twenty-first centuries, which prompted extensions of the sig- azarae, which successfully invaded agroecosystems. Similarly,
modontine known distribution. For example, the genus the forest mouse Akodon montensis is collected in abundance
Rhagomys, previously known from the Atlantic coastal Brazil- in secondary grown forests of Argentina, Brazil, and Paraguay.
ian state of Rio de Janeiro, has been reported from the east- In addition, some sigmodontines are commensal with humans.
ern slopes of the Peruvian Andes (Luna and Patterson, 2003). For example, Akodon reigi has been collected inside rural
A less spectacular example, although still remarkable was re- houses in Uruguay.
ported by Emmons in 1999, who collected in eastern Bolivia
specimens of Juscelinomys, a genus previously considered to be Microhabitat selection has been studied in relatively few
restricted to the Brazilian Federal District. sigmodontines. It was documented for three sympatric sig-
modontines from the Patagonian steppes. Abrothrix longipilis
266
A deer mouse (Peromyscus maniculatus) mother and five-day-old lit-
ter. (Photo by Tom McHugh/Photo Researchers, Inc. Reproduced by
permission.)

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Vol. 16: Mammals V Subfamily: Rats, mice, and relatives IV

size of the home range of A. cursor is neither affected by in-
dividual body size nor by population densities. Therefore, the
overlap of different individuals would increase at higher pop-
ulation densities. Similarly, males of Abrothrix olivaceus,
Akodon azarae, and Necromys lasiurus have larger home ranges
than females. On the other hand, males and females of Elig-
modontia morgani have home ranges of similar size.

A northern grasshopper mouse (Onychomys leucogaster) eating a lit- Behavior
tle pocket mouse (Perognathus longimembris) that it killed. It is the
only carnivorous North American rodent. (Photo by Tom McHugh/Photo Field and laboratory observations of sigmodontine behav-
Researchers, Inc. Reproduced by permission.) ior are scarce, and limited to a small number of species. There-
fore, no generalizations can be made.
prefers the steppe’s bushy patches, Eligmodontia morgani
prefers the bunchgrass patches, and Abrothrix olivaceus evenly Not much is known about sigmodontine social behavior;
distributes in both microenvironments. Similarly, in the hu- most reports are of anecdotic fashion. Wiedomys pyrrhorhinos
mid forest where it lives, the water rat Nectomys squamipes, may be gregarious, since eight adults and 13 young were found
prefers places close (< 10 m) to water courses with tree ferns in one termite nest. Similarly, Darwin reported six specimens
and exposed tree roots. of Calomys laucha were discovered in one burrow. The social
and gregarious habits of Phyllotis sublimis were described by
Bilenca and Kravetz (1999) studied in agroecosystems of Pearson (1951).
central Argentina the seasonal changes in microhabitat use by
the field mouse Akodon azarae and the vesper mouse Calomys From the patterns of trapping, it can be inferred that sig-
laucha. They showed that the structure of this sigmodontine modontines are mostly nocturnal. For example, the water
community is highly influenced by seasonal changes in habi- rat Nectomys squamipes is primarily active just after sunset.
tat structure and rodent abundance. In summer, both species Similarly, the rice rat Oryzomys intermedius remains sheltered
were equally distributed between the mature crop fields and during the day and becomes active at night. Several species,
their surrounding weedy borders. In the crop fields both such as the long-nosed mouse Oxymycterus nasutus and the
species preferred covered microhabitats and at the borders long-clawed mole mouse Geoxus valdivianus, are active both
they did not select microhabitats. In contrast, in winter there diurnally and nocturnally. Finally, other sigmodontines,
was sharp habitat segregation. The vesper mouse was nu- such as the long-nosed mouse Auliscomys boliviensis, are pri-
merically dominant in post-harvest crop fields and the field marily diurnal.
mouse was more abundant in borders. In addition, there were
clear differences in microhabitat selection at the borders, A. Sigmodontines use nests to shelter and to raise the young.
azarae occupying the more covered microhabitats and C. Nectomys squamipes and Oryzomys intermedius use dry leaves
laucha the less covered ones. and grasses to build nests that are egg-shaped, of about 6 in
long and 4 in wide (15 and 10 cm), and lack an obvious en-
Field ecology studies are scarce in sigmodontine literature; trance. Nests are usually placed at the end of tunnels of 4.0–12
therefore, basic information is lacking for most species. A field in (10–30 cm) long inside or under fallen logs. Less com-
study of the water rat Nectomys squamipes shows that its home
range covers 0.5–3.9 acres (0.2–1.6 ha). Similarly, Gentille A white-footed mouse (Peromyscus leucopus) in Ohio, USA. (Photo by
and collaborators (1997) showed that the size of the home Gary Meszaros/Photo Researchers, Inc. Reproduced by permission.)
range of the forest mouse Akodon cursor is seasonally constant,
and that on average covers 0.91 and 0.47 acres (0.37 and 0.19 267
ha). for males and females respectively. Females of A. cursor
are territorial while males are not. With males having a larger
territory, they have contact with several females, while females
would defend food and nesting resources. Interestingly, the

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Subfamily: Rats, mice, and relatives IV Vol. 16: Mammals V

White-footed mouse (Peromyscus leucopus) young in nest. (Photo by Maslowski/Photo Researchers, Inc. Reproduced by permission.)

monly, some nests are located between rocks or exposed tree Grooming behavior has been studied in Nectomys squamipes.
roots. N. squamipes nests closer to water courses than O. in- The water rat licks most reachable body parts, and grooms
termedius. Other species, such as Thomasomys aureus, build its face by circular movements of the forepaws.
their nests in trees. At the same time, other sigmodontines
take advantage of bird nests. This is the case of the red-nosed Little is known on sigmodontine communication. High-
tree rat Wilfredomys oenax that in Uruguay uses abandoned pitched vocalizations have been reported, mostly in anecdotic
nests of both the firewood-gatherer (Anumbius annumbi) and terms, for a few sigmodontines species, including Scapteromys
the golden-winged cacique (Cacicus chrysopterus) as diurnal aquaticus, S. tumidus, and Nectomys squamipes. Dominance sta-
shelter. tus in the hispid cotton rat Sigmodon hispidus is communicated
by urinary and fecal odors.
There are limited data on sigmodontine dispersal. Dis-
perser individuals of Akodon azarae are in general smaller than Feeding ecology and diet
those that do not disperse, but they neither differ with respect
to sex nor with reproductive condition. The highest disper- Most of the information available on sigmodontine diet
sal rate occurs in autumn. The water rat Nectomys squamipes comes from analysis of stomach contents (in which, usually a
only makes short movements and exhibits limited migration. small number of individuals were studied) and not from field
observation or experimental studies. As expected from such a
Several sigmodontines including, among others, the rice diverse group, sigmodontines show a large range of diets. Sig-
rats Oryzomys couesi and O. palustris, the water rats of the gen- modontines are omnivorous (e.g., Zygodontomys brevicauda),
era Amphinectomys, Lundomys, Holochilus, and Nectomys, the grassivorous (e.g., Reithrodon typicus), primarily frugivorous
marsh rats of the genus Scapteromys, and the ichthyomyines (e.g., Thomasomys aureus), primarily granivorous (e.g., Elig-
are excellent swimmers and divers. By swimming and diving modontia typus), and primarily animalivorous (e.g., Oxymycterus
these sigmodontines are able to escape predators and to ex- nasutus, Rheomys mexicanus); still others consume large amounts
ploit surface and underwater resources. Other species, such of fungus (e.g., Chelemys macronyx).
as Sigmodon hispidus, are less skilled swimmers, swimming only
on the water surface (Cook et al., 2001). Grzimek’s Animal Life Encyclopedia

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Mice and rats of the ichthyomyine tribe are among the Sumichrast’s harvest mouse (Reithrodontomys sumichrasti) is a nat-
most distinctive sigmodontines with regard to their diet be- ural predator of the monarch butterfly (Danaus plexippus). (Photo by
cause they feed on aquatic organisms (Voss, 1988). In much Gregory G. Dimijian, M.D./Photo Researchers, Inc. Reproduced by per-
of the scientific literature ichthyomyines are referred to as the mission.)
fish-eating sigmodontines. However, though ichthyomyines
feed on fishes, they represent a relatively uncommon item of ter. Other sigmodontine species restrict reproduction to one
the ichthyomyine diet. Ichthyomyines primarily feed on or two specific parts of the year (seasonally active). Reithrodon
arthropods, of which the vast majority is part of the stream auritus concentrates breeding in spring and early summer. Lit-
benthic fauna, including crabs, amphipods, and several insect ter sizes vary from one to eight, with a mean of 4.5 embryos.
orders (larvae, ninphae, and adults). Other less common Sigmodontines are in general short-lived, and in several
ichthyomyine food items are tadpoles and salamanders. Ichthy- species at least one sex reaches sexual maturity in the same
omys exhibits feeding plasticity: in the lowlands, crabs are an season of birth. This is the case of Reithrodon auritus females.
important food item, while in the highlands, where crabs are Eligmodontia typus rarely live longer than 9 months; it reaches
absent, it may be largely insectivorous. sexual maturity at approximately 45 days (Pearson et al.,
1987).
After entering the water Ichthyomys pittieri uses its whiskers
to explore the substrate, searching for, and identifying live Information on the patterns of sigmodontine copulatory
prey. The rat attacks its prey when they move after being behavior is sparse. Calomys, however, is a relatively well known
touched. Small prey (up to 0.8 in long; 20 cm) are seized with genus in this regard. There is information on three of the 11
the forepaws and are usually eaten immediately, while sitting species of the genus. They display intravaginal penile thrust-
on its hindquarters in the shallow water. Larger prey are ing and multiple ejaculations, in combination with single or
pinned to the bottom with forepaws, bitten repeatedly until multiple pre-ejaculatory intromissions. Locks are either rare
moribund, and then carried out of the water where they are or absent. In addition, C. musculinus, a non-monogamous
consumed. species, undergoes a stereotyped precopulatory behavior
composed mostly of agonistic behaviors in which the female
The feeding behavior of the omnivorous water rat Necto- and the male play the aggressive and submissive roles, re-
mys squamipes was studied by observations of captive animals spectively (Laconi and Castro-Vasquez, 1998).
(Ernest and Mares, 1986). The rat picks up immobile items
(e.g., leaves) with the incisors, then sits back on its haunches A remarkable aspect of sigmodontine population dynamics
and holds the food in the forepaws, to bite and chew the food. is the massive population irruptions or outbreaks recorded in
Mobile items (e.g., cockroaches, Blattidae) are caught on the several parts of South America since the sixteenth century.
ground by jumping on it with the forepaws. Flying insects are These explosive increases in sigmodontine population abun-
caught close to the ground and eaten head first, and entirely. dance or density during a relatively short period have been
The water rat takes mobile prey in the water (e.g., tadpoles) called ratadas. Starting in 1522, 63 ratadas are well-documented
with the forepaws. After the prey is secured, it is eaten like in literature; these have occurred in Argentina, Brazil, Chile,
the immobile items. and Peru. The outbreak estimated densities of some sigmod-
ontines are as follows: Oryzomys xantheolus (range = 250–259
Combining analyses of stomach contents and cafeteria individuals per 2.5 acres [1 ha]), Abrothrix olivaceus (52–237),
tests, Castellarini and collaborators (1998) established that the Phyllotis darwini (30–225), Oligoryzomys longicaudatus (46–154),
vesper mouse Calomys venustus is omnivorous, and that it and Akodon azarae (115). As ratadas involve one to four species
shows a tendency to folivory in spring and autumn and to
granivory in summer. C. venustus does not consume the leaves 269
that are abundant in the habitat, or consume them in low pro-
portions, rather, it shows a high preference for seed con-
sumption under conditions of equal food availability.

Reproductive biology

Information on sigmodontine reproduction comes pri-
marily from observations recorded during specimen collec-
tions (e.g., external measurements, testes position, presence
of vaginal closure membranes, and number of embryos). From
these observations, inferences on the part of the year where
species are reproductively active, number of estrous cycles per
year, and litter size, are made. There are species that seem to
breed throughout the whole year; for example Zygodontomys
brevicauda reproduce continuously, even in habitats with
marked seasonality (e.g., dry and wet season). Litter size
ranges from one to 11, averaging 4.5. Similarly, Sigmodon
hispidus also breeds, at least in the warmer parts of its distri-
bution, during the whole year. It has one to 15 young per lit-

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Subfamily: Rats, mice, and relatives IV Vol. 16: Mammals V

simultaneously, the total combined sigmodontine density may native species were susceptible, or through direct competi-
be even higher. Naturalists noted that massive flowering and tion. Similarly, Megaroyzomys, another Galápagos endemic,
subsequent massed seeding of bamboos preceded several ro- became extinct presumably in historic times, through preda-
dent irruptions, so sigmodontine outbreaks became associated tion by introduced dogs, cats, pigs, and Rattus. Hunting pres-
with bamboo blooming. Later, it was shown that several sure may be considered as a minor threat affecting
ratadas are associated with rainfall peaks, some of which are sigmodontine conservation. Mann (1945) suggested that in
caused by El Niño Southern Oscillation disturbances. Both some Chilean areas extensive trapping may have seriously re-
types of ratadas occur with approximately equal frequency and duced the populations of Chinchillula.
appear geographically located. Brazil, southern Chile, and
southern Argentina are affected mainly by bamboo-associated Significance to humans
rodent outbreaks, while Peru, northern Chile, and northern
Argentina are affected by rainfall-associated outbreaks. Func- The importance of sigmodontines to humans cannot be
tionally, ratadas are the result of a population closely track- overstated. Some species cause much damage to agricultural
ing changes in the environment. However, as it was shown in lands and stored foods. For example, in Formosa Province,
studies of the leaf-eared mouse Phyllotis darwini, a species that Argentina, the water rat Holochilus chacarius is reported to
undergoes ratadas in semi-arid Chile, intrinsic factors such as damage banana, mandioca, and sugar cane plantations. Simi-
density-dependence variables and competitors or predators larly, in the Mexican state of Veracruz, the cotton rat Sig-
also play a key role in shaping the demographic dynamics of modon hispidus and rice rat Oryzomys couesi are plagues on sugar
these species. This evidence underscores the interplay of dif- cane plantations of such important magnitude that eradica-
ferent phenomena regulating reproduction and demography tion plans are being designed. It is estimated that a single in-
in natural populations. dividual of Calomys laucha or Akodon azarae, which consume
stored foods in farm and village structures, can eat 2.2 to 4.4
Finally, it is interesting to note that in nine species of lb (1–2 kg) of food per year.
Akodon (azarae, boliviensis, kofordi, mollis, montensis, puer, sub-
fuscus, torques, and varius) there are females with a XY pair of Other sigmodontines are the reservoirs of the etiological
sexual chromosomes (and not XX as is typical in mammals; agents of a number of human diseases. In South America, all
XY females also occur in the arvicolines Dycrostonix torquatus, hantaviruses known to cause Hantavirus Pulmonary Syn-
Microtus cabrearae, and Myopus schisticolor). The prevalence in drome are associated with species of sigmodontine rodents,
wild populations of these heterogametic females ranges from including different long-tailed mice of the genus Oligoryzomys,
30 to 60%. These females are fertile. XY sex reversed females the field mice Necromys benefactus and Akodon azarae, the ves-
are assumed to occur due to a deficient expression of the Y per mouse Calomys laucha, and the cotton rat Sigmodon alstoni.
chromosome linked gene Sry, resulting in the developing of In addition, the vertebrate reservoir of the Machupo virus,
ovaries instead of testes. the etiological agent of the Bolivian hemorrhagic fever, is a
non described species of vesper mouse (Calomys). Similarly,
Conservation status the reservoir of the Junin and Guanarito viruses, which cause
the Argentine and Venezuelan hemorrhagic fevers, are, re-
In April 2003 the IUCN Red List of Threatened Species spectively, the vesper mouse Calomys musculinus and the cane
listed 54 sigmodontine species. Three sigmodontines, Neso- mouse Zygodontomys brevicauda. Finally, it has been shown that
ryzomys darwini, N. indefessus, and Oryzomys nelsoni, are con- the forest mouse Akodon montensis, the long-tailed mouse Olig-
sidered to be extinct; four other species, Nectomys parvipes, oryzomys nigripes, the subterranean mouse Thaptomys nigrita,
Oryzomys gorgasi, Rhagomys rufescens, and Sigmodontomys and the rice rat Oryzomys russatus are reservoirs of Borrelia-
aphrastus, are listed as Critically Endangered. Ten sigmod- like spirochetes which cause a Lyme disease simile.
ontines species are considered Endangered, 13 Vulnerable,
one species Near Threatened, and 19 to be at Lower Risk. On the other hand, many sigmodontines species are ben-
Data are deficient to evaluate the status of four species. For eficial to man by the role played in ecosystems. Some are key-
the sole fact that the understanding of species limits of most stone species in maintaining the vigor of ecosystems, through
sigmodontine genera is far from being settled, these figures their role in dispersing seeds (e.g., Oryzomys intermedius)
are subject to change. For instance, instead of subsuming Ory- and/or being prey of many medium- and large-sized verte-
zomys galapagoensis under O. bauri, Dowler et al. (2000) rec- brates (e.g., owls, snakes, and other carnivores). Other species
ognize both forms as distinct Galápagos endemic species. This are directly exploited by man. For example, the chinchilla
classificatory scheme implies that another sigmodontine mouse Chinchillula is trapped for its thick, soft, and silky fur.
species, O. galapagoensis that has not been collected since 1835, Trimmings and robes are made of these skins. Remarkably,
should be regarded as extinct. one of these robes may contain more than 150 skins. Zoo-
archeological work indicates that during the Holocene period,
One of the major sigmodontine threats is habitat destruc- sigmodontines did not represent a food item for the indige-
tion due to land conversion for urbanization and agricultural nous peoples that lived in the areas that are now known as
and logging expansion. Another important threat is the in- the Argentinean Patagonia and Pampas. However, present
troduction of exotic fauna. For instance, the most likely cause Mbyá Guaraníes from Misiones, Argentina hunt and eat sig-
of the extinction of the Galápagos endemic Nesoryzomys dar- modontines. Finally, some species play an increasing role as
wini and N. indefessus is the introduction of black rats (Rattus “domestic animals” used in medical research; this is the case
rattus), either through the introduction of pathogens to which of Calomys laucha and C. musculinus.

270 Grzimek’s Animal Life Encyclopedia

2 1
4 3
5
6

7
8

1. Chilean tree mouse (Irenomys tarsalis); 2. Hispid cotton rat (Sigmodon hispidus); 3. Water mouse (Chibchanomys orcesi); 4. Marsh rice rat
(Oryzomys palustris); 5. Rio de Janeiro rice rat (Phaenomys ferrugineus); 6. Kemp’s grass mouse (Deltamys kempi); 7. Andean mouse (Andino-
mys edax); 8. Brazilian shrew mouse (Blarinomys breviceps). (Illustration by Barbara Duperron)

Grzimek’s Animal Life Encyclopedia 271

Subfamily: Rats, mice, and relatives IV Vol. 16: Mammals V

Species accounts

Rabbit rat HABITAT

Reithrodon auritus Most common in steppes and prairies. However, the rabbit rat
inhabits a wide range of environments, including beech forests,
TAXONOMY sparse shrub lands, bunchgrass prairies, dense grasslands, culti-
vated fields, overgrazed pastures, sandy coasts, and stony hills.
Reithrodon auritus (Fischer, 1814), Buenos Aires Province, Ar-
gentina. Tribe Reithrodontini. BEHAVIOR

OTHER COMMON NAMES Active both diurnally and nocturnally year-round. Activity be-
gins in the evening and lasts until the early hours of the morn-
Spanish: Rata conejo. ing. Reithrodon excavates tunnels of 1.6–2.8 in (4–7 cm) in
diameter. It also uses tunnels made by other animal such as
PHYSICAL CHARACTERISTICS those of tuco-tucos (Ctenomys).

Total length 8.3–10.6 in (212–269 mm), tail length 3.3–4.0 in FEEDING ECOLOGY AND DIET
(84–103 mm), ear length 0.6–1.1 in (15–29 mm). Weight
0.7–4.1 oz (20.5–116 g). Pelage color varies from dark brown The diet consists only of grasses.
to pale buffy gray dorsally, and from white to brownish ochre-
ous ventrally. Eyes and ears are large. It has four pairs of mam- REPRODUCTIVE BIOLOGY
mary glands. Hind legs are very long. Upper incisors have two
frontal grooves. Molars are markedly high. Females reach reproductive maturity at about two months of
age. Males reach maturity later than females. Specimens repro-
DISTRIBUTION ductively active have been collected in spring and summer (Sep-
tember to March). Most gravid females were found in spring.
Patagonian region of Argentina, from Tierra del Fuego and Litter size ranges from one to eight. Juveniles were found in
southern Chile to 36ºS. North of 36ºS is restricted to a few spring and in higher numbers during summer and autumn.
high-altitude (> 6,562 ft; > 2,000 m) localities in central and
northern Argentina. There is an unconfirmed record from CONSERVATION STATUS
Malvinas Islands.
Not threatened. Populations are protected in several Argen-
tinean and Chilean national parks and reserves.

SIGNIFICANCE TO HUMANS

In the Argentinean Province of Buenos Aires the rabbit rat is
considered a pest because it eats large amounts of grass. ◆

Chibchanomys orcesi Kemp’s grass mouse
Reithrodon auritus
Sigmodon hispidus Deltamys kempi

272 TAXONOMY

Deltamys kempi Thomas, 1917, Isla Ella, Delta of the Parana
River, Argentina. Tribe Akodontini.

OTHER COMMON NAMES

Spanish: Ratón aterciopelado.

PHYSICAL CHARACTERISTICS

Measurements of the holotype. Total length 6.9 in (174 mm),
tail length 3.3 in (85 mm), ear length 0.5 in (13 mm), length
of foot without claws 0.9 in (22 mm). Eyes are small and
barely visible, ears are narrow. The soft pelage is blackish
brown dorsally and dull brownish gray ventrally. Tail is faintly
bicolored.

DISTRIBUTION

Small area of southeastern South America, from northeast
Buenos Aires Province and southern Entre Ríos Province in
Argentina, throughout south, central east, and northeast
Uruguay, to the Atlantic coast of the Rio Grande do Sul State
in Brazil.

HABITAT

Marshy areas, especially edges of wetlands, flooded grass-
lands, and places with reeds and straws. In Uruguay also in-
habits, although less abundantly, some woodlands. In

Grzimek’s Animal Life Encyclopedia

Vol. 16: Mammals V Subfamily: Rats, mice, and relatives IV

Deltamys kempi OTHER COMMON NAMES
Irenomys tarsalis
Blarinomys breviceps Spanish: Rata arrocera, coludo.

PHYSICAL CHARACTERISTICS

Total length 8.9–12.0 in (225–305 mm), tail length 3.9–6.9 in
(100–175 mm), hindfoot length 1.1–1.5 in (28–37 mm).
Weight 1.4–3.0 oz (40–85 g). Generalized rat-like appearance.
Dorsal coloration range varies from grayish brown to gray.
The venter is much lighter. The underfur is water repellent.
Eight pairs of mammary glands. The forefoot and hindfoot
have four and five toes, respectively. Tail is scaly, long, and
nearly naked.

DISTRIBUTION

Endemic to the United States, ranging from southeastern
Pennsylvania and southern New Jersey to the tip of Florida
and westwards to eastern Texas. There are records from south-
ern Kentucky and Illinois, southwestern Missouri, and south-
eastern Oklahoma.

HABITAT

Common in wetlands, including marshes at the Atlantic and
Gulf coasts. It also inhabits swamps, meadows, and prairies.

BEHAVIOR

Semiaquatic, being good swimmers and divesr. Primarily noc-
turnal. High-pitched squeaks were associated with agonistic be-
havior upon females by males in captivity. It constructs
spherical grassy nests to sleep in during the day.

FEEDING ECOLOGY AND DIET

Carnivorous, but also feeds on seeds, succulent plant parts, and
fungus. Food items may vary seasonally upon resource avail-

Argentina it has also been collected in tall grass coastal areas
and gallery forest.

BEHAVIOR

Probably fossorial. It rests under grasses and leaves.

FEEDING ECOLOGY AND DIET

Mostly carnivorous. Insect remains have been recorded in
stomachs of Argentinean and Uruguayan specimens. In addi-
tion, seeds and remains of green plants have been found in
stomachs of specimens collected in Uruguay.

REPRODUCTIVE BIOLOGY

Little is known on reproductive aspects of Kemp’s grass
mouse. Litter size may be three since that numbers of young
were found in one nest in Argentina and another in Uruguay.

CONSERVATION STATUS

In Argentina it is considered rare and at lower risk. Uruguayan
populations are considered not threatened. The status of
Brazilian populations is not known.

SIGNIFICANCE TO HUMANS

None known. ◆

Marsh rice rat Andinomys edax
Oryzomys palustris
Oryzomys palustris Phaenomys ferrugineus

TAXONOMY 273

Oryzomys palustris (Harlan, 1837), near Salem, New Jersey,
United States. Tribe Oryzomyini.

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Subfamily: Rats, mice, and relatives IV Vol. 16: Mammals V

ability. Animal items vary, but insects, fiddler crabs, snails are CONSERVATION STATUS
the most common; other animal items are fishes, clams, eggs,
and young of long-billed marsh wrens. Not threatened.

REPRODUCTIVE BIOLOGY SIGNIFICANCE TO HUMANS

Breeding may occur throughout the year, although it may be None known. ◆
low during hot summer months. Gestation period lasts be-
tween 21 and 28 days. Different average litter size has been re- Brazilian shrew mouse
ported, 3.6, 4.8, and 5. Newborn weigh around 0.1 oz (3.5 g).
Weaning occurs at age 11–20 days. Sexual maturity is reached Blarinomys breviceps
between 40 and 45 days of age. Life expectancy is generally
less than one year. TAXONOMY

CONSERVATION STATUS Blarinomys breviceps (Winge, 1887), Rio das Velhas, Minas
Gerais State, Brazil. Tribe Akodontini.
Not threatened.
OTHER COMMON NAMES
SIGNIFICANCE TO HUMANS
Portuguese: Rato do Mato.
Reservoir of the Bayou hantavirus, a pathogenic virus associ-
ated with human pulmonary syndrome. ◆ PHYSICAL CHARACTERISTICS

Chilean tree mouse Total length 5.1–6.3 in (129–161 mm), tail length 1.2–2.0 in
(30–52 mm), hindfoot length 0.6–0.8 in (16–21 mm), ear
Irenomys tarsalis length 0.3–0.4 in (8–10 mm). Shrewlike; superficially resembles
the North American insectivore genus Blarina, and hence its
TAXONOMY scientific generic name. Pelage is dark gray. Head is short and
conical. Eyes extremely reduced. Claws well developed.
Irenomys tarsalis (Philippi, 1900), Fundo San Juan, Valdivia
Province, Chile. Formerly placed in the phyllotine tribe. DISTRIBUTION

OTHER COMMON NAMES First known from the Brazilian states of Bahia, Espiritu Santo,
Minas Gerais, and Rio de Janeiro States; it has also been recov-
Spanish: Ratón arbóreo, laucha arbórea. ered from owl pellets in the Argentinean province of Misiones.

PHYSICAL CHARACTERISTICS HABITAT

Total length 10.6–12.8 in (270–326 mm), tail length 3.5–7.7 in Montane forest.
(90–196 mm), hindfoot length 1.1–1.3 in (28–32 mm), ear
length 0.8–1.0 in (20–25 mm). Weight 1.1–2.4 oz (30–67 g). BEHAVIOR
Dorsal coloration is grayish cinnamon. The venter is washed
with pinkish cinnamon buff. Ears are brownish black. Tail is Primarily fossorial.
blackish brown, and it may be paler on the ventral side; it ends
in a penciled tip. Upper incisors are grooved. FEEDING ECOLOGY AND DIET

DISTRIBUTION Carnivorous. Stomachs of two specimens contained arthropods
of six different orders, mostly insects (90%) but also arachnids.
Although vernacularly known as the Chilean tree mouse, Ireno-
mys tarsalis is not endemic to Chile, it also has populations in REPRODUCTIVE BIOLOGY
Argentina. In Chile it ranges from Chillán (VII Región) south
to Puerto Ibañez (XI Región), including Chiloe Island and the Little is known. Males with scrotal testes were collected in Jan-
Guaitecas Islands. In Argentina distributes in along the western uary and February. Pregnant females were trapped in Septem-
side of Neuquen, Río Negro, and Chubut Provinces. ber, January, and February. Observed number of embryos has
been one or three.
HABITAT
CONSERVATION STATUS
Generally confined to humid, temperate forested habitats, es-
pecially bamboo stands or shrubby areas, although it is also Listed as Lower Risk/Near Threatened.
present in the interface between forest and steppe.
SIGNIFICANCE TO HUMANS
BEHAVIOR
None known. ◆
Nocturnal. It appears docile when removed from traps. After
release it often climbs bamboo or trees, although it may run Andean mouse
across the forest floor.
Andinomys edax
FEEDING ECOLOGY AND DIET
TAXONOMY
Granivorous and frugivorous, although also eats green vegeta-
tion, fungi, and seeds. Andinomys edax Thomas, 1902, El Cabrado, Potosi Depart-
ment, Bolivia. Formerly placed in the phyllotine tribe.
REPRODUCTIVE BIOLOGY
OTHER COMMON NAMES
Breeding occurs in spring but may extend into summer. Birth
takes place in summer. Litter size ranges from three to six. Spanish: Rata andina.

274 PHYSICAL CHARACTERISTICS

Total length 10.1–12.4 in (257–315 mm), tail length 4.2–6.3 in
(107–160 mm), hindfoot length 1.2–1.3 in (30–32 mm), ear

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Vol. 16: Mammals V Subfamily: Rats, mice, and relatives IV

length 0.9–1.1 in (22–27 mm). Heavy-bodied. Pelage soft, lax, SIGNIFICANCE TO HUMANS
upperparts and sides drab, underparts gray. The tail is thinly
haired and sharply bicolored. Feet are well developed. None known. ◆

DISTRIBUTION Rio de Janeiro rice rat

High-altitude regions of northwestern Argentina, Bolivia, Phaenomys ferrugineus
northern Chile, and southern Peru.
TAXONOMY
HABITAT
Phaenomys ferrugineus (Thomas, 1984), Rio de Janeiro, Brazil.
It lives in the puna in dense vegetation near water courses and Formerly placed in the Thomasomyine tribe.
bushy thickets.
OTHER COMMON NAMES
BEHAVIOR
Portuguese: Rato do mato ferrugíneo.
Nocturnal; terrestrial, but may also be scansorial. It nests in-
side round holes carpeted with fine straw. PHYSICAL CHARACTERISTICS

FEEDING ECOLOGY AND DIET Measurements of the holotype: total length 13.2 in (335 mm),
tail length 7.4 in (187 mm), hindfoot length 1.3 in (34 mm), ear
Feeds on green herbs. length 0.7 in (17 mm). Pelage is dorsally rust-colored, cheeks
and sides are lighter, and the underparts are whitish. Ears are
REPRODUCTIVE BIOLOGY small and well furred. The tail is unicolored, dark gray.

Breeds at the end of the dry season. A female collected by O. DISTRIBUTION
Pearson on December 18 had three well-developed embryos.
Known only from three localities in the Brazilian states of Rio
CONSERVATION STATUS de Janeiro and San Pablo.

Not threatened. HABITAT

SIGNIFICANCE TO HUMANS One specimen collected in 1998 was trapped in herbaceous
vegetation in an area that is considerably altered for agriculture
None known. ◆ and pasture. The collection site is in a valley surrounded by
forested hills that have been selectively logged.
Water mouse
BEHAVIOR
Chibchanomys orcesi
Nothing is known.
TAXONOMY
FEEDING ECOLOGY AND DIET
Chibchanomys orcesi Jenkins and Barnett, 1997, Las Cajas, Azuay
Province, Ecuador. Tribe Ichthyomyini. Nothing is known.

OTHER COMMON NAMES REPRODUCTIVE BIOLOGY

Spanish: Rata acuática. Nothing is known.

PHYSICAL CHARACTERISTICS CONSERVATION STATUS

Total length 8.3–9.0 in (211–229 mm), tail length 4.3–4.8 in Listed as Critically Endangered by the IUCN.
(108–122 mm), hindfoot length 0.8–0.9 in (19–24 mm), ear
length 0.4–0.6 in (9–14 mm). Weight 1.2–1.4 oz (35–40 g). SIGNIFICANCE TO HUMANS
Pelage is soft, dense, and woolly, dark brownish gray dorsally,
and light gray ventrally. Ears and eyes are reduced. The tail is None known. ◆
longer than head and body.
Hispid cotton rat
DISTRIBUTION
Sigmodon hispidus
Known only from three localities in the Las Cajas Plateau,
Ecuador. TAXONOMY

HABITAT Sigmodon hispidus Say and Ord, 1825, St. Johns River, Florida,
United States. Tribe Sigmodontini.
High altitude páramo (10,170–13,100 ft; 3,100–4,000 m), close
to fast-flowing streams. OTHER COMMON NAMES

BEHAVIOR Spanish: Rata de campo; rata algodonera.

Semiaquatic. PHYSICAL CHARACTERISTICS

FEEDING ECOLOGY AND DIET Total length 8.8–14.4 in (224–365 mm), tail length 3.2–6.5 in
(81–166 mm), hindfoot length 1.1–1.6 in (28–41 mm), ear
Primarily an aquatic insectivore, but also eats fish. length 0.6–0.9 in (16–24 mm). Weight 3.5–8.0 oz (100–225 g).
Pelage is grizzled with blackish or dark brownish hairs. Under-
REPRODUCTIVE BIOLOGY parts are pale to dark grayish. Tail is dark. Female possesses
five pairs of mammae; however, females with six and four pairs
Nothing is known. It appears to be a scarce páramo inhabitant. have also been found.

CONSERVATION STATUS 275

Not known, but Barnett (1997) noted that the Las Cajas
Plateau, the only place from where C. orcesi is known, may be-
come severely impacted by human activities in the near future.

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Subfamily: Rats, mice, and relatives IV Vol. 16: Mammals V

DISTRIBUTION size varies from one to 15, with animals from northern popula-
tions having larger litters. Neonates are well developed at
Inhabits the three Americas; from southeast United States birth; their eyes open within 36 hours after birth and are
(south Nebraska, central Virginia, southeast Arizona, peninsu- weaned in 10–15 days. Males reach reproduction maturity in
lar Florida), through interior and east Mexico through Central two or three months; females reach it earlier, even in 10 days
America, to northern Colombia and Venezuela. and in an average of 30–40 days. Females normally produce
several litters per year.
HABITAT
CONSERVATION STATUS
Usually an inhabitant of grass dominated landscapes.
The subspecies S. h. eremicus and S. h. insulicola are considered
BEHAVIOR at Lower Risk/Near Threatened by the IUCN.

Both diurnal and nocturnal, and is able to swim. SIGNIFICANCE TO HUMANS

FEEDING ECOLOGY AND DIET Sigmodon hispidus has been used as a biomonitor to assess envi-
ronmental contamination. Sigmodon hispidus is the reservoir of
Feeds primarily on grasses. There are data showing that it se- two strains of hantavirus called Black Creek Canal virus and
lects food items and combines them into a nutritious diet. It Muleshoe viruses; these are pathogenic viruses associated with
does not hoard food. human pulmonary syndrome. ◆

REPRODUCTIVE BIOLOGY

Breeding is through the year; however, differences exist in rela-
tion to latitude. Gestation lasts approximately 27 days. Litter

276 Grzimek’s Animal Life Encyclopedia

Vol. 16: Mammals V Subfamily: Rats, mice, and relatives IV

Common name / Physical Habitat and Distribution Conservation
Scientific name/ characteristics behavior Diet status
Other common names
Allen's woodrat Long, narrow head. Upperparts are Dry wooded slopes, tropical Southernmost Sinaloa Coco-oil seeds along Lower Risk/
Hodomys alleni reddish brown to dusky brown. Under- deciduous forest, rocky to Oaxaca; interior with other types of Near Threatened
parts are white to buff. Tail from dusky to outcrops to dense scrub. Mexico along basin of seeds, crabs.
White-throated woodrat white. Head and body length 14.5–17.5 Little known of reproductive Rio Balsas to central
Neotoma albigula in(36.8–44.5 cm), tail length 6.2–8.1 in habits. Females produce one Puebla.
German: WÏstenratte (15.8–20.6 cm). to two offspring.

Bushy-tailed woodrat Coloration is brownish gray, underside is Desert habitats, where they Extreme southeastern Mainly cacti. Not threatened
Neotoma cinerea white to gray. Tail is brownish gray on build nests in rocky areas, California to southern
German: Buschschwanzratte top, lighter on bottom. Feet are white. under shrubs, small trees, or Colorado to western
Head and body length 12.9 in (32.8 cm), cacti. Breeding season from Texas, United States,
Eastern woodrat weight 7.6 oz (215 g). January to August, two or south to northeastern
Neotoma floridana more litters per season. Michoacan and
Nocturnal, solitary, and western Hidalgo,
Dusky-footed woodrat territorial. Mexico.
Neotoma fuscipes
Coloration varies across range, from A variety of habitats, from Southeast Yukon and Consists mainly of Not threatened
Golden mouse buff to darker. White coloration around boreal woodlands to deserts. westernmost North- vegetable matter, such as
Ochrotomys nuttalli the feet. Average male weight 14.3 oz Litter size is usually three west Territories, south woody plants, and
(405 g), female weight 9.5 oz (270 g) offspring. Build constructs through British arthropods.
Southern grasshopper mouse called middens, do not Columbia and western
Onychomys torridus hibernate. Alberta, Canada, to
northwestern United
Big-eared climbing rat States, as far south as
Ototylomys phyllotis northern New Mexico
and Arizona and east
to western Dakotas.

Coloration is brown around base of neck Wooded marshes, grass- South-central and Leaves, bark, fruits, and Not threatened
to dark brown and black on rump. Nasal lands, and coastal plains. eastern United States seeds.
area is pink. Body is small, compact. Litter size ranges from two from east-central
to seven offspring. Breeding Colorado to eastern
season varies with Texas, eastwards along
geographic location. Appalachians to
Nocturnal and solitary, western Connecticut,
except during breeding and along Gulf-Coast
season. states to southern
North Carolina and
central Florida.

Coloration is cinnamon with tints of buff On hillsides, valleys, and Western Oregon Seventy-two different Not threatened
and pink. Ears are thin, large, rounded, close to water. Avoid open
and broad. Claws are short. Head and grassland and open oak through western and types of plants.
body length 15.2–17.4 in (38.5–44.3 woods with little underbrush.
cm), weight 8.1–10.6 oz (230–300 g). Nocturnal, uses branches for central California,
travel.
United States, to

northern Baja California,

Mexico.

Coloration of fur is gold, underparts are Thick woodlands, swampy Southeastern Missouri Mainly seeds. Not threatened
white, tail is cream. Cheeks contain thick areas, among vines, and across to southern
folds of enamel. Head and body length within small trees and Virginia, south to
2–4.5 in (5.1–11.5 cm), tail length shrubs. Reproduces all year; eastern Texas, the Gulf
2–3.8 in (5–9.7 cm). nocturnal and solitary. Coast, and central
Florida.

Fine, dense fur, gray or pinkish cinnamon Found within burrow Central California, Seeds, plants, and Not threatened
in color. Underside of tail is white. Head systems in the ground. Most southern Nevada, and vegetables.
and body length 3.5–5.1 in (9–13 cm), reproductive activity extreme southwestern
tail length 1.2–2.4 in (3–6 cm). between late spring and Utah, United States,
summer. Extremely south to northern Baja
aggressive, nocturnal, good California, western
climbers. Sonora, and northern-
most Sinaloa, Mexico.

Coloration is gray and brown on dorsal Tropical forests, both dry Central Costa Rica Fruits and leaves. Not threatened
side, white and gray on the ventral side. and wet, with abundant rocks north to Yucatán
Hands and feet are pale. Tail is long, or rocky ledges. Nocturnal Peninsula, southern
hairless, covered with scares, from dark and arboreal. Tabasco, and northern
gray/brown to a paler color on ventral Chiapas, Mexico;
surface. Eyes and ears are large and isolated record from
hairless. Head and body length 3.7–7.5 in north-central Guerrero,
(9.5–19 cm), tail length 3.9–7.5 in Mexico.
(10–19 cm).

Grzimek’s Animal Life Encyclopedia 277

Subfamily: Rats, mice, and relatives IV Vol. 16: Mammals V

Common name / Physical Habitat and Distribution Conservation
Scientific name/ characteristics behavior Diet status
Other common names
Texas mouse Coloration of dorsal side is brown with Rocky areas including cliffs Edwards Plateau of Seeds, fruits, flowers, Not threatened
Peromyscus attwateri darker and blackish marks mixed in. and limestone outcrops with north-central Texas, nuts, and other plant
Underside is lighter. Head and body woody vegetation. Breeding north through eastern products.
California mouse length 7.8 in (19.8 cm), weight 0.9–1.2 season from late September Oklahoma, to south-
Peromyscus californicus oz (25–35 g). to winter. Four offspring per eastern Kansas, south-
litter. western Missouri, and
northwestern Arkansas,
United States.

Coloration is yellowish brown or gray Dense chaparral and broad- Central and southern Fruits, seeds, and flowers Not threatened
mixed with black dorsal coloring. Under- sclerophyll woodland. California, United of shrubs.
parts are white. Fulvous throat patch and Nocturnal, poor burrower, States, excluding San
lateral line are present. Head and body breeding occurs year-round. Joaquin Valley, to
length 8.7–11.2 in (22–28.5 cm), tail northwestern Baja
length 4.6–6.1 in (11.7–15.6 cm), weight California Norte,
1.2–1.9 oz (33.2–54.4 g). Mexico.

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of Philander frenata and Akodon cursor in a Brazilian Restinga (1977): 227–241.
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Resources (Muroidea: Muridae) from the Galápagos Islands, Ecuador.”
Smithsonian Contributions on Paleobiology 51 (1982): 1–23.
Smith, M. F., and J. L. Patton. “Phylogenetic Relationships Voss, R. “Systematics and Ecology of Ichthyomyines Rodents
and the Radiation of Sigmodontine Rodents in South (Muroidea): Patterns of Morphological Evolution in a Small
America: Evidence from Cytochrome b.” Journal of Adaptative Radiation.” Bulletin of the American Museum of
Mammalian Evolution 6 (1999): 89–128. Natural History 188 (1988): 259–493.

Steadman, D. W., and C. E. Ray. “The Relationships of Guillermo D’Elía, PhD
Megaoryzomys curioi, an Extinct Cricetine Rodent

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Rats, mice, and relatives V

All other rats, mice, and relatives

Class Mammalia Distribution
Order Rodentia Found throughout Africa, Madagascar, and Asia, including Europe
Suborder Sciurognathi
Family Muridae

Thumbnail description
The 13 remaining subfamilies of Muridae are
incredibly diverse ecologically, behaviorally, and
morphologically

Size
The more than 213 species in the 13 remaining
subfamilies of Muridae vary in size from small,
mouse-sized animals to bamboo rats
(Rhizomyinae), which can reach 8.8 lb (4 kg) in
weight

Number of genera, species
47 genera; approximately 213 species

Habitat
Habitats range from deserts to dense, tropical
forests; there are animals that specialize for
burrowing underground, hopping across loose
soils, and climbing in trees

Conservation status
Critically Endangered: 18 species; Endangered:
12 species; Vulnerable: 18 species; Lower
Risk/Near Threatened: 27 species; Data
Deficient: 1 species

Evolution and systematics and from very common to very rare. Murid fossils are known
from the Oligocene to recent in North America and Eurasia,
The rodent family Muridae is the largest mammalian fam- from the Pliocene until recent in South America, and more
ily. Murids occur on nearly all landmasses, except for some recently in Africa, Madagascar, and Australia.
arctic and oceanic islands, New Zealand, Antarctica, and parts
of the West Indies. Morphological, ecological, behavioral, di- The relationships among all subfamilies of Muridae (in-
etary, and taxonomic diversity in murids is truly astonishing. cluding those not covered here: Murinae, Sigmodontinae,
Murids range from solitary animals to highly social animals Cricetinae, and Arvicolinae) are poorly understood. Careful

The greater Malagasy bushy-tailed rat (Eliurus tanala) foraging. (Photo A red forest rat (Nesomys rufus) eating a mushroom. (Photo by Har-
by Harald Schütz. Reproduced by permission.) ald Schütz. Reproduced by permission.)

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Subfamily: Rats, mice, and relatives V Vol. 16: Mammals V

A white-throated wood rat (Neotoma albigula) foraging among the cactuses of Arizona, USA. (Photo by G. C. Kelley/Photo Researchers, Inc. Re-
produced by permission.)

examination of morphological characters, especially cranial Gerbils (Meriones unguiculatus) have a number of different coat col-
and dental characters, has not been able to elucidate patterns ors. (Photo by Carolyn A. McKeone/Photo Researchers, Inc. Repro-
of relationship among the various subfamilies, although some duced by permission.)
affinities were identified. Carleton and Musser (1984), in their
exhaustive morphological work, preferred to treat relation-
ships among all murid subfamilies as unresolved.

Recent systematic work using molecular characters has
helped to resolve patterns of evolutionary relationships among
many murid subfamilies. Although some murid subfamilies
(Lophiomyinae and Platacanthomyinae) have yet to be included
in a molecular analysis, DNA sequences of representative mem-
bers of all other subfamilies have been generated and analyzed
within a systematic framework. Nearly all currently recognized
murid subfamilies retain their rank as distinct lineages in these
analyses. The fossorial lineages, Spalacinae and Rhizomyinae,
appear to share a common ancestor with all of the remaining
subfamilies. The remaining subfamilies form several groups of
related lineages. A primarily African group (including Mada-
gascar) includes Nesomyinae, Petromyscinae, Cricetomyinae,
Dendromurinae, and Mystromyinae. Calomyscinae appears as
its own lineage; the remaining subfamilies form two large lin-
eages. A group made up mainly of Arvicolinae, Sigmodonti-
nae, and Cricetinae includes the subfamily Myospalacinae.
The final cluster is made up of the subfamilies Murinae (in-

282 Grzimek’s Animal Life Encyclopedia

Vol. 16: Mammals V Subfamily: Rats, mice, and relatives V

A male gerbil (Meriones unguiculatus). (Photo by Carolyn A. McKeone/
Photo Researchers, Inc. Reproduced by permission.)

An ice rat or Sloggett’s vlei rat, (Otomys sloggetti) basking in the sun Habitat
outside its burrow. (Photo by Peter Chadwick/Photo Researchers, Inc.
Reproduced by permission.) Murids in these subfamilies occupy a wide variety of habi-
tats and niches. Most are terrestrial but some live under-
cluding Otomyinae), Acomyinae (previously included within ground, in trees, are semi-aquatic, or live in extreme
Murinae), and Gerbillinae. environments. Most notable in this respect are the ger-
billines, which have become adapted to extreme aridity.
Physical characteristics They avoid water loss and heat stress by being active at night,
seeking refuge during the day in burrows, maintaining high
The murid species in these subfamilies vary widely in size relative humidity in their burrows, and producing concen-
and other physical features. Most species are small and mouse- trated urine. Gerbillinae is the most diverse of the 13 sub-
sized, usually with moderately long tails and a generally
brownish fur color. However, many species have adopted fos-
sorial modes of life, becoming large and robust, with reduced
eyes and ears, and teeth and limbs modified for digging. Oth-
ers, in particular the gerbillines, have become adapted to a
nocturnal existence in primarily arid landscapes. These species
are capable of jumping locomotion as a result of enlarged and
modified hind limbs. They also have greatly enlarged audi-
tory bullae, resulting in an extraordinarily keen sense of hear-
ing. Species in several of the subfamilies strongly resemble
other murid rodents such as voles (Arvicolinae) and hamsters
(Cricetinae), and members of other rodent families such as
pocket gophers (Geomyidae), dormice (Gliridae), jumping
mice (Zapodidae), and jerboas (Dipodidae), illustrating the
evolutionary plasticity of these groups.

Distribution A large bamboo rat (Rhizomys sumatrensis) forages on the ground.
(Photo by L. Bruce Kekule/Photo Researchers, Inc. Reproduced by per-
These 13 subfamilies are found throughout Africa, Mada- mission.)
gascar, and Asia, including Europe.
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Subfamily: Rats, mice, and relatives V Vol. 16: Mammals V

families, illustrating how successful this suite of adaptations
has proven.

Behavior

Members of these 13 murid subfamilies vary widely in the
social structures and behaviors. Many are solitary, but some
species are highly social, with complex modes of communi-
cation. Most are active primarily at night, although some are
active either throughout the day, or are diurnal.

Feeding ecology and diet

Dietary diversity in these groups ranges from animals that
eat mainly invertebrates to those that eat all kinds of plant
matter, and some that eat vertebrates. The typical diet is made
up of primarily seeds, but includes fruits, shoots, leaves, and
animal matter. The fossorial subfamilies Rhizomyinae,
Spalacinae, and Myospalacinae eat mainly roots and other un-
derground plant parts, rarely venturing aboveground. The di-
versity in dental patterns in these groups, particularly of the
cheek teeth, reflects this dietary breadth.

A Malagasy reed rat (Brachyuromy betsileonensis) foraging. (Photo by Reproductive biology
Harald Schütz. Reproduced by permission.)
Reproductive patterns and behavior in these groups are
quite variable. Breeding can occur seasonally or throughout
the year and the number of offspring can range from one to
many. In general, multiple young are born on a seasonal ba-
sis and the young develop quickly, achieving both indepen-
dence and sexual maturity at an early age. However, there are
exceptions. Males are typically not involved in raising young.

A western Malagasy bushy-tailed rat (Eliurus myoxinus) feeding on a A jird or gerbil (Meriones unguiculatus) found in Mongolia. (Photo by
tree trunk. (Photo by Harald Schütz. Reproduced by permission.) Tom McHugh/Photo Researchers, Inc. Reproduced by permission.)

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Very little is known about the specifics of mating behaviors Significance to humans
in the majority of species.
Species within this very diverse group include human com-
Conservation status mensals, agricultural pests, food animals, research animals,
and pets. More importantly, almost all of the species in these
Many species in this diverse set of subfamilies are abundant 13 subfamilies are important members of the ecosystems in
and may be human commensals and agricultural pests. How- which they live. Many small rodents in this group are among
ever, habitat destruction or human persecution threatens many the most abundant small mammals in their communities,
species. Animals that are restricted to small ranges or particu- forming an important prey base for small and large predators.
lar habitats may be especially vulnerable. For example, mem- Many species are also important in nutrient cycling and seed
bers of the Petromyscinae tend to be restricted to small, relict dispersal. Finally, research on the incredible array of evolu-
distributions and are vulnerable to habitat changes. Especially tionary trajectories and adaptations found in these subfami-
notable in this regard are the members of the Nesomyinae, lies will continue to yield rich and valuable insights into
which are all restricted to portions of Madagascar. This rodent evolutionary processes and patterns of animal diversity. Murid
radiation is truly unique and nearly all of the species in this rodents are some of the primary animal models used in the
group are critically threatened by profound, human-induced analysis of human diseases and genetics, and a better under-
habitat destruction throughout Madagascar. Although the Ger- standing of murid evolution and ecology directly impacts so-
billinae is the most diverse of the 13 subfamilies, many species ciety’s ability to solve problems related to human health and
within this particular subfamily are threatened or Endangered. well-being.

Grzimek’s Animal Life Encyclopedia 285

12

3
4

5

6
7

1. Mouse-like hamster (Calomyscus bailwardi); 2. White-tailed mouse (Mystromys albicaudatus); 3. Pygmy rock mouse (Petromyscus collinus); 4.
Sundevall’s jird (Meriones crassus); 5. Gray climbing mouse (Dendromus melanotis); 6. Malagasy giant rat (Hypogeomys antimena); 7. Gambian
rat (Cricetomys gambianus). (Illustration by Brian Cressman)

286 Grzimek’s Animal Life Encyclopedia

12

3
4

5
6

1. Malabar spiny dormouse (Platacanthomys lasiurus); 2. Angoni vlei rat (Otomys angoniensis); 3. Crested rat (Lophiomys imhausi); 4. Siberian
zokor (Myospalax myospalax); 5. Palestine mole rat (Nannospalax ehrenbergi); 6. Large bamboo rat (Rhizomys sumatrensis). (Illustration by Brian
Cressman)

Grzimek’s Animal Life Encyclopedia 287